Remove meters from storage list when removed and handle NoRecordedValue flag when removing meters

[stonkie]

Fixes #5950
Design discussion issue #

Changes

This allows clean Dispose of Meter objects which will send NoRecordedValue data points to close the series (e.g. send a staleness marker to prometheus). It also fixes the internal storage leak which would prevent frequent rotation of the metrics.

NOTE : A significant refactoring of the protobuf serialization merged right after I created this PR, so I had to redo a significant part of the change on Dec 4th.

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)

[linux-foundation-easycla]

The committers listed above are authorized under a signed CLA.

• ✅ login: stonkie / name: Kevin Coulombe (aeb1639, d12808d, cc18547, c9d5475, 2823545, e4e377e, 04a3eee, f4fa00b, 57bf5d0, 60aa3db, 30dca16, 8ab84af, c2dfaea)
• ✅ login: rajkumar-rangaraj / name: Rajkumar Rangaraj (12f4541)

[Kielek]

Hi @stonkie, thanks for the contribution.
Signing EasyCLA is hard requirement before we can accept contribution.

[codecov]

Codecov Report

Attention: Patch coverage is 37.50000% with 30 lines in your changes missing coverage. Please review.

Project coverage is 83.95%. Comparing base (e3665c9) to head (c9d5475).

Files with missing lines	Patch %	Lines
...tryProtocol/Implementation/MetricItemExtensions.cs	16.66%	30 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #5997      +/-   ##
==========================================
- Coverage   84.14%   83.95%   -0.20%     
==========================================
  Files         275      275              
  Lines       12560    12603      +43     
==========================================
+ Hits        10569    10581      +12     
- Misses       1991     2022      +31     

Flag	Coverage Δ
unittests-Project-Experimental	83.82% <37.50%> (-0.28%)	⬇️
unittests-Project-Stable	83.94% <37.50%> (-0.09%)	⬇️

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

Files with missing lines	Coverage Δ
src/OpenTelemetry/Metrics/Metric.cs	97.26% <100.00%> (+0.01%)	⬆️
...rc/OpenTelemetry/Metrics/Reader/MetricReaderExt.cs	92.24% <100.00%> (+0.42%)	⬆️
...tryProtocol/Implementation/MetricItemExtensions.cs	82.66% <16.66%> (-11.21%)	⬇️

... and 4 files with indirect coverage changes

---- 🚨 Try these New Features:

• Flaky Tests Detection - Detect and resolve failed and flaky tests

[stonkie]

@Kielek : I'm going through the motions to get this done at my company and there are more hoops than I expected. EasyCLA will probably wait until Monday.

[stonkie]

Discussions during SIG meeting led to asking to feature flag the NoRecordedValue DataPoint to avoid changing working behavior. I'll add that and adjust the tests asap.

[stonkie]

I'm not exactly sure how to format the changelog entry. Should I create an entry without version number or release date?

[Kielek]

I'm not exactly sure how to format the changelog entry. Should I create an entry without version number or release date?

Please put it under unreleased section.

## Unreleased

* Your description goes here.
  And here if it is long enough.
  ([#5997](https://github.com/open-telemetry/opentelemetry-dotnet/pull/5997))

```

[stonkie]

@Kielek Thanks, it's done.