Rollback #8232 and #8204

[arjan-bal]

These changes are causing integration issues with an internal cipher implementation, see cl/745109957. The changes will be rolled forward when the cipher implementation is fixed.

RELEASE NOTES: N/A

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 82.13%. Comparing base (25c7509) to head (be7fef4).
Report is 1 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #8236      +/-   ##
==========================================
+ Coverage   82.06%   82.13%   +0.07%     
==========================================
  Files         412      412              
  Lines       40503    40491      -12     
==========================================
+ Hits        33238    33257      +19     
+ Misses       5892     5866      -26     
+ Partials     1373     1368       -5     

Files with missing lines	Coverage Δ
credentials/alts/internal/conn/common.go	100.00% <100.00%> (ø)
credentials/alts/internal/conn/record.go	82.55% <100.00%> (+4.34%)	⬆️
credentials/alts/internal/handshaker/handshaker.go	69.58% <100.00%> (-6.19%)	⬇️

... and 28 files with indirect coverage changes

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