feat: add WIP metrics SDK

[dyladan]

This is the start of a ground-up rewrite of the metrics SDK. Even if we decide not to move forward with #2598 I think it makes sense to rethink the SDK from the beginning.

[codecov]

Codecov Report

Merging #2601 (f2d79aa) into main (7d67bf3) will increase coverage by 0.38%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##             main    #2601      +/-   ##
==========================================
+ Coverage   92.87%   93.26%   +0.38%     
==========================================
  Files          98      115      +17     
  Lines        3662     4645     +983     
  Branches      831     1036     +205     
==========================================
+ Hits         3401     4332     +931     
- Misses        261      313      +52     

Impacted Files	Coverage Δ
...es/opentelemetry-context-zone-peer-dep/src/util.ts	100.00% <0.00%> (ø)
...telemetry-sdk-trace-web/src/StackContextManager.ts	94.28% <0.00%> (ø)
...-sdk-trace-web/src/enums/PerformanceTimingNames.ts	100.00% <0.00%> (ø)
...opentelemetry-exporter-trace-otlp-http/src/util.ts	100.00% <0.00%> (ø)
...s/opentelemetry-instrumentation-fetch/src/fetch.ts	96.98% <0.00%> (ø)
packages/opentelemetry-sdk-trace-web/src/types.ts	100.00% <0.00%> (ø)
...ation-xml-http-request/src/enums/AttributeNames.ts	100.00% <0.00%> (ø)
...emetry-instrumentation-xml-http-request/src/xhr.ts	97.58% <0.00%> (ø)
...entelemetry-sdk-trace-web/src/WebTracerProvider.ts	100.00% <0.00%> (ø)
...exporter-metrics-otlp-http/src/transformMetrics.ts	95.65% <0.00%> (ø)
... and 7 more

[legendecas]

👍 for a new wip package so that we can move forward at a fast pace.

[aabmass]

I understand this PR is not meant to be complete, so feel to address some of the comments in later PRs if that's easier

[vmarchaud]

LGTM when #2601 (comment) is resolve

[dyladan]

/easycla

[pirgeo]

Very optional, but I think having the links to the respective spec pages is great. Just adding these here for completeness, we could however always add them later (or remove them if we don't want them).