Get opentelemetry trace id from request headers instead of creating a new trace

[kozistr]

What does this PR do?

Fixes #2376

I made a simple middleware to extract OpenTelemetry context (e.g. trace id, span id) from request headers. When valid transparent info is provided, then, it'll gonna use that context to create the span (if not, it'll generate its own as it does currently).

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Who can review?

Anyone in the community is free to review the PR once the tests have passed. Feel free to tag
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@OlivierDehaene OR @Narsil

[kozistr]

@Narsil @OlivierDehaene @ErikKaum hi! if you have the bandwidth, could you by any chance review this PR? thanks!

related PR: huggingface/text-embeddings-inference#425