Make otlp-http, otlp-grpc, and otlp-common gems production-ready

[kaylareopelle]

The exporter/otlp-http, exporter/otlp-grpc and exporter/otlp-common directories in this repository reference tests to break out the existing opentelemetry-exporter-otlp gem into smaller chunks. Ruby doesn't currently have support for a gRPC exporter, and the behavior that would be shared between an HTTP and gRPC exporter would live in a common gem they both rely on.

Initial PRs related to this work:

• Split otlp exporter #1179
• feat: Otlp grpc #1180

These exporters are not production ready as they currently exist. (See: #1337)

Contributions welcome to add test coverage, error handling, and other work to make this production-ready.

[github-actions]

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