Implement SDK metrics for trace

[anuraaga]

I am helping implement the SDK metrics spec. Exporter metrics for all signals have already been implemented, this starts on the tracer side. A very similar PR will come later for logs, and a less similar one for metrics

https://opentelemetry.io/docs/specs/semconv/otel/sdk-metrics/

[codecov[bot]]

Codecov Report

:x: Patch coverage is 91.98113% with 17 lines in your changes missing coverage. Please review. :white_check_mark: Project coverage is 90.09%. Comparing base (0e646e8) to head (af0de7a). :warning: Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
...a/io/opentelemetry/sdk/trace/SdkTracerMetrics.java	82.14%	12 Missing and 3 partials :warning:
...telemetry/sdk/trace/export/BatchSpanProcessor.java	87.50%	1 Missing and 1 partial :warning:

Additional details and impacted files

@@             Coverage Diff              @@
##               main    #7895      +/-   ##
============================================
- Coverage     90.10%   90.09%   -0.01%     
- Complexity     7325     7360      +35     
============================================
  Files           825      829       +4     
  Lines         22051    22219     +168     
  Branches       2179     2185       +6     
============================================
+ Hits          19868    20018     +150     
- Misses         1504     1517      +13     
- Partials        679      684       +5     

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[jack-berg]

FYI this is a copy of #7441 and #7430, which was opened right before I was out on leave. Since I came back I've been preoccupied with other things and lost track of it. I feel bad about that @JonasKunz.

Now we've got 2 PRs doing the same thing and I'm not sure there's a fair way to proceed.

Edit: maybe its some consolation if I make a concerted effort to get this reviewed and merged this time around.