[otlp] OTLP Exporter Custom serializer Part 1 - WritingPrimitives

[rajkumar-rangaraj]

Fixes Part of #5730
Design discussion issue #

Changes

Please provide a brief description of the changes here.
Based on prototype - #5731

Merge requirement checklist

• CONTRIBUTING guidelines followed (license requirements, nullable enabled, static analysis, etc.)
• Unit tests added/updated
• Appropriate CHANGELOG.md files updated for non-trivial changes
• Changes in public API reviewed (if applicable)

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 86.36%. Comparing base (6250307) to head (c7fc344).
Report is 356 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #5910      +/-   ##
==========================================
+ Coverage   83.38%   86.36%   +2.97%     
==========================================
  Files         297      258      -39     
  Lines       12531    11345    -1186     
==========================================
- Hits        10449     9798     -651     
+ Misses       2082     1547     -535     

Flag	Coverage Δ
unittests	?
unittests-Project-Experimental	86.34% <100.00%> (?)
unittests-Project-Stable	86.05% <100.00%> (?)

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
...ol/Implementation/Serializer/ProtobufSerializer.cs	100.00% <100.00%> (ø)

... and 239 files with indirect coverage changes

[CodeBlanch]

I'm not going to drop a comment everywhere for this, but it might make sense to remove all of this expansion logic. Just assume the buffer has room. If not, catch indexoutofrange exception upstream, expand the buffer, and retry the entire serialization operation. This is what we do in prometheus. Why? Once we get to stable buffer size it will be a lot of faster without needing to do these checks each time we write some tiny piece of data into the blob. Also we can move from ref byte[] everywhere to just byte[].

[CodeBlanch]

LGTM