Merge the Lightstep Metrics SDK

[jmacd]

Description: This merges the work covered in PRs:

#171
#172
#173
#174
#175
#183
#184
#185
#190
#191
#195

Link to tracking Issue: LS-29760

Testing: The SDK is completely unit-tested. Manual integration testing with lightstep has been done.

Thanks: Thanks to @MadVikingGod for substantial early feedback on the design of the Lightstep metrics SDK. Thanks to @jaronoff97 @njvrzm @paivagustavo @codeboten for reivews.

[jmacd]

I am officially stuck (from my machine):

ERRO Running error: 1 error occurred:
	* can't run linter goanalysis_metalinter: failed to pre-run gofmt: failed to validate analyzers: analyzer "gofmt" has nil Run

or (from CI)_

level=warning msg="[runner] Can't run linter goanalysis_metalinter: failed to pre-run errcheck: failed to validate analyzers: analyzer \"errcheck\" has nil Run"

[jmacd]

After disabling the linters, I've found some flakey test failures.

[codecov-commenter]

Codecov Report

Merging #196 (d2d4b8f) into main (d233da9) will increase coverage by 3.92%.
The diff coverage is 95.14%.

@@            Coverage Diff             @@
##             main     #196      +/-   ##
==========================================
+ Coverage   90.72%   94.65%   +3.92%     
==========================================
  Files           7       62      +55     
  Lines         485     3234    +2749     
==========================================
+ Hits          440     3061    +2621     
- Misses         26      131     +105     
- Partials       19       42      +23     

Impacted Files	Coverage Δ
pipelines/common.go	100.00% <ø> (ø)
...k/metric/exporters/otlp/internal/otlpconfig/tls.go	41.66% <41.66%> (ø)
...k/metric/aggregator/aggregation/category_string.go	50.00% <50.00%> (ø)
lightstep/sdk/metric/number/kind_string.go	50.00% <50.00%> (ø)
lightstep/sdk/metric/sdkinstrument/kind_string.go	50.00% <50.00%> (ø)
...p/sdk/metric/aggregator/aggregation/temporality.go	55.55% <55.55%> (ø)
pipelines/metrics.go	67.18% <65.21%> (-13.31%)	⬇️
lightstep/sdk/metric/exporters/otlp/exporter.go	67.34% <67.34%> (ø)
...etric/aggregator/aggregation/temporality_string.go	75.00% <75.00%> (ø)
...tric/exporters/otlp/internal/otlpconfig/options.go	82.20% <82.20%> (ø)
... and 51 more

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[jaronoff97]

Woooo very excited!! Thank you so much!