Optimize the size and pointer bytes for pdata structs

[bogdandrutu]

There are 2 things that matters for structs:

1. The overall size - which to ensure minimum size we need to ensure fields are sorted by their alignment (not necessary size).
2. The pointer bytes - how many bytes of the object that the GC has to potentially scan for pointers. pointers and struct with pointers should be first.

We could probably modify the generator to do this, but it is simpler to run a tool like betteralign.

Field alignment is important for pdata structs because these are on the data path and they are generated for each message we process.

/Users/bdrutu/github/opentelemetry-collector/pdata/internal/generated_proto_exemplar.go:52:15: 24 bytes saved: struct with 48 pointer bytes could be 24
/Users/bdrutu/github/opentelemetry-collector/pdata/internal/generated_proto_exponentialhistogramdatapoint.go:77:36: 8 bytes saved: struct of size 216 could be 208
/Users/bdrutu/github/opentelemetry-collector/pdata/internal/generated_proto_exponentialhistogramdatapointbuckets.go:18:43: 8 bytes saved: struct with 16 pointer bytes could be 8
/Users/bdrutu/github/opentelemetry-collector/pdata/internal/generated_proto_exportlogspartialsuccess.go:18:31: 8 bytes saved: struct with 16 pointer bytes could be 8
/Users/bdrutu/github/opentelemetry-collector/pdata/internal/generated_proto_exportmetricspartialsuccess.go:18:34: 8 bytes saved: struct with 16 pointer bytes could be 8
/Users/bdrutu/github/opentelemetry-collector/pdata/internal/generated_proto_exportprofilespartialsuccess.go:18:35: 8 bytes saved: struct with 16 pointer bytes could be 8
/Users/bdrutu/github/opentelemetry-collector/pdata/internal/generated_proto_exporttracepartialsuccess.go:18:32: 8 bytes saved: struct with 16 pointer bytes could be 8
/Users/bdrutu/github/opentelemetry-collector/pdata/internal/generated_proto_histogramdatapoint.go:74:25: 48 bytes saved: struct with 176 pointer bytes could be 128
/Users/bdrutu/github/opentelemetry-collector/pdata/internal/generated_proto_ipaddr.go:17:13: 8 bytes saved: struct with 32 pointer bytes could be 24
/Users/bdrutu/github/opentelemetry-collector/pdata/internal/generated_proto_keyvalue.go:17:15: 8 bytes saved: struct with 32 pointer bytes could be 24
/Users/bdrutu/github/opentelemetry-collector/pdata/internal/generated_proto_keyvalueandunit.go:20:22: 8 bytes saved: struct of size 32 could be 24
/Users/bdrutu/github/opentelemetry-collector/pdata/internal/generated_proto_location.go:18:15: 16 bytes saved: struct with 48 pointer bytes could be 32
/Users/bdrutu/github/opentelemetry-collector/pdata/internal/generated_proto_logrecord.go:20:16: 64 bytes saved: struct with 120 pointer bytes could be 56
/Users/bdrutu/github/opentelemetry-collector/pdata/internal/generated_proto_mapping.go:18:14: 32 bytes saved: struct with 40 pointer bytes could be 8
/Users/bdrutu/github/opentelemetry-collector/pdata/internal/generated_proto_numberdatapoint.go:49:22: 16 bytes saved: struct with 64 pointer bytes could be 48
/Users/bdrutu/github/opentelemetry-collector/pdata/internal/generated_proto_profile.go:20:14: 64 bytes saved: struct with 136 pointer bytes could be 72
/Users/bdrutu/github/opentelemetry-collector/pdata/internal/generated_proto_requestcontext.go:68:21: 16 bytes saved: struct with 48 pointer bytes could be 32
/Users/bdrutu/github/opentelemetry-collector/pdata/internal/generated_proto_resource.go:18:15: 8 bytes saved: struct with 40 pointer bytes could be 32
/Users/bdrutu/github/opentelemetry-collector/pdata/internal/generated_proto_resourceprofiles.go:18:23: 8 bytes saved: struct with 88 pointer bytes could be 80
/Users/bdrutu/github/opentelemetry-collector/pdata/internal/generated_proto_sample.go:19:13: 8 bytes saved: struct of size 88 could be 80
/Users/bdrutu/github/opentelemetry-collector/pdata/internal/generated_proto_scopelogs.go:18:16: 16 bytes saved: struct with 96 pointer bytes could be 80
/Users/bdrutu/github/opentelemetry-collector/pdata/internal/generated_proto_scopemetrics.go:18:19: 16 bytes saved: struct with 96 pointer bytes could be 80
/Users/bdrutu/github/opentelemetry-collector/pdata/internal/generated_proto_scopeprofiles.go:18:20: 16 bytes saved: struct with 96 pointer bytes could be 80
/Users/bdrutu/github/opentelemetry-collector/pdata/internal/generated_proto_scopespans.go:18:17: 16 bytes saved: struct with 96 pointer bytes could be 80
/Users/bdrutu/github/opentelemetry-collector/pdata/internal/generated_proto_span.go:20:11: 16 bytes saved: struct of size 216 could be 200
/Users/bdrutu/github/opentelemetry-collector/pdata/internal/generated_proto_spancontext.go:18:18: 8 bytes saved: struct of size 56 could be 48
/Users/bdrutu/github/opentelemetry-collector/pdata/internal/generated_proto_spanevent.go:20:16: 8 bytes saved: struct with 32 pointer bytes could be 24
/Users/bdrutu/github/opentelemetry-collector/pdata/internal/generated_proto_spanlink.go:21:15: 24 bytes saved: struct with 48 pointer bytes could be 24
/Users/bdrutu/github/opentelemetry-collector/pdata/internal/generated_proto_summarydatapoint.go:20:23: 32 bytes saved: struct with 64 pointer bytes could be 32
/Users/bdrutu/github/opentelemetry-collector/pdata/internal/generated_proto_tcpaddr.go:17:14: 16 bytes saved: struct with 40 pointer bytes could be 24
/Users/bdrutu/github/opentelemetry-collector/pdata/internal/generated_proto_udpaddr.go:17:14: 16 bytes saved: struct with 40 pointer bytes could be 24

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 92.10%. Comparing base (45c4476) to head (1046d03).
⚠️ Report is 3 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #14339      +/-   ##
==========================================
- Coverage   92.11%   92.10%   -0.01%     
==========================================
  Files         668      668              
  Lines       41363    41363              
==========================================
- Hits        38100    38098       -2     
- Misses       2226     2227       +1     
- Partials     1037     1038       +1     

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