adding metrics semconv

[brettmc]

Generate some initial metrics SemConv files. I've chosen to start small, with just http and otel groups until we need more, and thought one file per group seemed neater.

Closes: #1613

[brettmc]

When this is merged, I think we should create an issue to update our metrics generation from span and log processors to use the otel semconv attributes. They didn't exist when we first implemented.

[brettmc]

Any opinions on how I've split each group into its own file?

[ChrisLightfootWild]

Any opinions on how I've split each group into its own file?

I think I prefer it this way 👍

I'm not entirely sure on the units of measure though, although I see they are coming directly from the schemas - so maybe not much we could do with them. e.g. Unit: {connection}

[Nevay]

Any opinions on how I've split each group into its own file?

The spec suggests a similar structure:

├── SchemaUrls.code
├── attributes
│ ├── ClientAttributes.code
│ ├── HttpAttributes.code
│ └── ...
├── metrics
│ ├── HttpMetrics.code
│ └── ...
└── events
└── ...

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 68.64%. Comparing base (5451d57) to head (a31ee11).
Report is 5 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff              @@
##               main    #1633      +/-   ##
============================================
- Coverage     68.68%   68.64%   -0.05%     
  Complexity     2854     2854              
============================================
  Files           425      425              
  Lines          8699     8699              
============================================
- Hits           5975     5971       -4     
- Misses         2724     2728       +4     

Flag	Coverage Δ
8.5	68.64% <ø> (-0.05%)	⬇️

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