feat: add opentelemetry-exporter-http-transport package

[herin049]

Description

Adds a common opentelemetry-exporter-http-transport package that will be utilized by multiple HTTP exporter packages (initially OTLP JSON) to abstract away and generalize underlying HTTP transport implementations and exporting with OTLP. Introducing this package will significantly reduce the amount of code duplication present in HTTP exporters and will allow for the usage of alternative HTTP client libraries.

Fixes #3439, #4171, #1003, #2990

Type of change

Please delete options that are not relevant.

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

How Has This Been Tested?

uv run tox -e py314-test-opentelemetry-exporter-http-transport

Does This PR Require a Contrib Repo Change?

• Yes. - Link to PR:
• No.

Checklist:

• Followed the style guidelines of this project
• Changelogs have been updated
• Unit tests have been added
• Documentation has been updated

[codeboten]

This is really exciting. Thanks @herin049, just one question regarding the naming

[codeboten]

If this is specific to otlp over http, should the package name reflect that: opentelemetry-exporter-otlp-http-transport

[herin049]

I was actually debating this exact naming decision, I decided that opentelemetry-exporter-http-transport might be slightly more appropriate than opentelemetry-exporter-otlp-http-transport given that we might want to use the transport abstraction for non-OTLP exporters (e.g. Jaeger). That being said, I still opted to include the OTLPHTTPClient inside this package since it's pretty lean and will be reused by the Proto + JSON HTTP exporters, but we could even break this off into another package, but my thought is this would be a bit overkill. WDYT?