Instrument the otlpmetrichttp exporter

[tongoss]

resolve: #7011

Benchmarks

➜ benchstat /tmp/bench_disabled.txt /tmp/bench_enabled.txt
goos: darwin
goarch: arm64
pkg: go.opentelemetry.io/otel/exporters/otlp/otlpmetric/otlpmetrichttp
cpu: Apple M1 Max
                                         │ /tmp/bench_disabled.txt │       /tmp/bench_enabled.txt       │
                                         │         sec/op          │   sec/op     vs base               │
ExporterExportMetrics/NoObservability-10               105.0µ ± 0%   106.5µ ± 0%  +1.37% (p=0.000 n=30)
ExporterExportMetrics/Observability-10                               108.3µ ± 0%
geomean                                                105.0µ        107.4µ       +1.37%

                                         │ /tmp/bench_disabled.txt │       /tmp/bench_enabled.txt        │
                                         │          B/op           │     B/op      vs base               │
ExporterExportMetrics/NoObservability-10              27.68Ki ± 0%   27.69Ki ± 0%  +0.05% (p=0.000 n=30)
ExporterExportMetrics/Observability-10                               27.70Ki ± 0%
geomean                                               27.68Ki        27.69Ki       +0.05%

                                         │ /tmp/bench_disabled.txt │       /tmp/bench_enabled.txt        │
                                         │        allocs/op        │ allocs/op   vs base                 │
ExporterExportMetrics/NoObservability-10                444.0 ± 0%   444.0 ± 0%       ~ (p=1.000 n=30) ¹
ExporterExportMetrics/Observability-10                               444.0 ± 0%
geomean                                                 444.0        444.0       +0.00%
¹ all samples are equal

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 86.3%. Comparing base (86e673c) to head (0c7a31e).

Additional details and impacted files

@@           Coverage Diff           @@
##            main   #7493     +/-   ##
=======================================
+ Coverage   86.2%   86.3%   +0.1%     
=======================================
  Files        295     299      +4     
  Lines      25864   26120    +256     
=======================================
+ Hits       22307   22566    +259     
+ Misses      3184    3180      -4     
- Partials     373     374      +1     

Files with missing lines	Coverage Δ
exporters/otlp/otlpmetric/otlpmetrichttp/client.go	80.4% <100.0%> (+0.8%)	⬆️
...pmetric/otlpmetrichttp/internal/counter/counter.go	100.0% <100.0%> (ø)
.../otlpmetrichttp/internal/observ/instrumentation.go	100.0% <100.0%> (ø)
...tlp/otlpmetric/otlpmetrichttp/internal/x/observ.go	100.0% <100.0%> (ø)
...ers/otlp/otlpmetric/otlpmetrichttp/internal/x/x.go	100.0% <100.0%> (ø)

... and 3 files with indirect coverage changes

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[flc1125]

The overall quality is very high. There are some minor issues.

[flc1125]

Additionally, for the benchmarking part, can we provide before and after comparison data?

[tongoss]

Additionally, for the benchmarking part, can we provide before and after comparison data?

For sure, please find benchmark results as below:

➜ benchstat /tmp/bench_disabled.txt /tmp/bench_enabled.txt
goos: darwin
goarch: arm64
pkg: go.opentelemetry.io/otel/exporters/otlp/otlpmetric/otlpmetrichttp
cpu: Apple M1 Max
                                         │ /tmp/bench_disabled.txt │       /tmp/bench_enabled.txt       │
                                         │         sec/op          │   sec/op     vs base               │
ExporterExportMetrics/NoObservability-10               105.0µ ± 0%   106.5µ ± 0%  +1.37% (p=0.000 n=30)
ExporterExportMetrics/Observability-10                               108.3µ ± 0%
geomean                                                105.0µ        107.4µ       +1.37%

                                         │ /tmp/bench_disabled.txt │       /tmp/bench_enabled.txt        │
                                         │          B/op           │     B/op      vs base               │
ExporterExportMetrics/NoObservability-10              27.68Ki ± 0%   27.69Ki ± 0%  +0.05% (p=0.000 n=30)
ExporterExportMetrics/Observability-10                               27.70Ki ± 0%
geomean                                               27.68Ki        27.69Ki       +0.05%

                                         │ /tmp/bench_disabled.txt │       /tmp/bench_enabled.txt        │
                                         │        allocs/op        │ allocs/op   vs base                 │
ExporterExportMetrics/NoObservability-10                444.0 ± 0%   444.0 ± 0%       ~ (p=1.000 n=30) ¹
ExporterExportMetrics/Observability-10                               444.0 ± 0%
geomean                                                 444.0        444.0       +0.00%
¹ all samples are equal

[flc1125]

Please resolve the conflict.