New runtime/metrics instrumentation

[jmacd]

Description:
Uses the new-since go-1.16 runtime/metrics package to generate metrics, intended to replace the otel-go-contrib instrumentation/runtime package.

Link to tracking Issue:
Part of #257. Part of #270.

Testing: Full coverage.

Documentation: doc.go lists the metrics generated as of go-1.19. This does not build prior to go-1.18.

[codecov-commenter]

Codecov Report

Base: 94.06% // Head: 93.63% // Decreases project coverage by -0.42% ⚠️

Coverage data is based on head (4e6791f) compared to base (9f0728e).
Patch coverage: 81.60% of modified lines in pull request are covered.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #267      +/-   ##
==========================================
- Coverage   94.06%   93.63%   -0.43%     
==========================================
  Files          67       68       +1     
  Lines        3538     3663     +125     
==========================================
+ Hits         3328     3430     +102     
- Misses        161      181      +20     
- Partials       49       52       +3     

Impacted Files	Coverage Δ
lightstep/instrumentation/runtime/builtin.go	81.60% <81.60%> (ø)

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[jaronoff97]

Fantastic add, excited to get this in our codebase!