Separate OTLP HTTP and GRPC Exporters

[Sherlouk]

Closes #389

Created three targets: Common, Grpc, and HTTP. The latter two are also products.
The default product (same name as previous) will use Grpc to aide in backwards compatibility.

Clients using HTTP will have to change imports, but given the experimental nature of the current implementation I don't believe this to be a major problem. However, if others disagree we could make the default product include both Grpc and HTTP and then have separate GRPC and HTTP targets for those who specifically only want one.

Updated sample code which proves we're able to drop the NIO and GRPC dependencies. Not done full benchmarks, but locally the sample product does build quicker.

No other changes beyond separation and imports. Basic compile tests done, but not a full integraiton.

[codecov]

Codecov Report

Patch coverage: 100.00% and project coverage change: +0.10 🎉

Comparison is base (a7004d0) 68.04% compared to head (cb8b704) 68.14%.

❗ Current head cb8b704 differs from pull request most recent head d1155cc. Consider uploading reports for the commit d1155cc to get more accurate results

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #399      +/-   ##
==========================================
+ Coverage   68.04%   68.14%   +0.10%     
==========================================
  Files         253      253              
  Lines       11820    11820              
==========================================
+ Hits         8043     8055      +12     
+ Misses       3777     3765      -12     

Impacted Files	Coverage Δ
...TelemetryProtocolCommon/common/EnvVarHeaders.swift	97.36% <ø> (ø)
...s/OpenTelemetryProtocolCommon/common/Headers.swift	100.00% <ø> (ø)
...metryProtocolCommon/common/OtlpConfiguration.swift	100.00% <ø> (ø)
...elemetryProtocolCommon/logs/LogRecordAdapter.swift	100.00% <ø> (ø)
...ryProtocolCommon/trace/utils/TraceProtoUtils.swift	22.22% <ø> (ø)
...enTelemetryProtocolGrpc/logs/OtlpLogExporter.swift	92.30% <ø> (ø)
...emetryProtocolGrpc/metric/OtlpMetricExporter.swift	93.33% <ø> (ø)
...elemetryProtocolGrpc/trace/OtlpTraceExporter.swift	93.18% <ø> (ø)
...etryProtocolGrpc/trace/OtlpTraceJsonExporter.swift	88.57% <ø> (ø)
...porters/OpenTelemetryProtocolHttp/HTTPClient.swift	93.75% <ø> (ø)
... and 8 more

... and 2 files with indirect coverage changes

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[nachoBonafonte]

Looks really good to me, thanks a lot for your contribution

[nachoBonafonte]

Hi Sherlouk, after merging a previous PR (#331 ) it brought some conflicts with your code, could you resolve it?, it might need some code in both exporters now. I will merge after done

[Sherlouk]

Will try and find some time to rebase, little strapped for time though now as I'll be on holiday for the next week 👍

Have tested it locally though and am happy with functionality.