feat(node-sdk): add spanProcessors option

[naseemkullah]

Which problem is this PR solving?

Since registered span processors are chained together via that active multispanprocessor, it makes sense to expose the option as an array of span processors. As such this change also deprecates the spanProcessor option in favor of the new, more flexiblespanProcessors option.

use case: suppose you are happy with the default batchspan processor, but rather not override any of its hooks and just add a subsequent processor that does something e.g. extracts baggage and adds the baggage entries to spans (side note: an off the shelf baggage extractor span processor might be nice!).

Fixes # (issue)

Short description of the changes

add a spanProcessors config option. convert the original/deprecated spanProcessor config to an array of one if used. we now loop over the spanProcessors and register them to the tracer provider.

n.b. if someone so happens to set both spanProcessor and spanProcessors it will default to using the latter, non deprecated option

Type of change

Please delete options that are not relevant.

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

How Has This Been Tested?

Please describe the tests that you ran to verify your changes. Provide instructions so we can reproduce. Please also list any relevant details for your test configuration

• The main span processor test now tests that an array is passed in successfully.

Checklist:

• Followed the style guidelines of this project
• Unit tests have been added modified
• Documentation has been updated

[codecov]

Codecov Report

Merging #4454 (c8c3072) into main (2df6310) will increase coverage by 0.05%.
The diff coverage is 100.00%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4454      +/-   ##
==========================================
+ Coverage   92.37%   92.43%   +0.05%     
==========================================
  Files         304      330      +26     
  Lines        8682     9504     +822     
  Branches     1831     2026     +195     
==========================================
+ Hits         8020     8785     +765     
- Misses        662      719      +57     

Files	Coverage Δ
...imental/packages/opentelemetry-sdk-node/src/sdk.ts	93.18% <100.00%> (+0.38%)	⬆️

... and 40 files with indirect coverage changes

[naseemkullah]

This is now ready for review. As per today's SIG this adds the spanProcessors (array) option to node-sdk

[pichlermarc]

Thanks @naseemkullah 🙂
Looks good % nits

[naseemkullah]

Thanks @pichlermarc!

[hectorhdzg]

Related to #4451, it would be good to add LogProcessors as well.