[otlp-transformer] rethink depending on all signal SDKs for OTLP transformation

[pichlermarc]

Currently, we depend on all signals in the @opentelemetry/otlp-transformer package. We should find a way to either eliminate these dependencies or split the package up so that each signal transformation only uses the signal's SDK package.

See related PRs/Issues #3798 and #3794

This issue is considered done when:

• a decision is made whether the current state is okay or not
• if the current state is not okay, follow-up issues with concrete steps have been created to address this.

[github-actions]

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