Flatten OTEL logs to ingest on Parseable

[nikhilsinhaparseable]

Fixes #312

enhancement to add feature to flatten otel logs to be able to ingest on Parseable

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This PR has:

• been tested to ensure log ingestion and log query works.
• added comments explaining the "why" and the intent of the code wherever would not be obvious for an unfamiliar reader.
• added documentation for new or modified features or behaviors.

[Eshanatnight]

I think it's better if we implement serde deserialize trait for the structs, or else it looks overwhelming

[Eshanatnight]

I think it's better if we implement serde deserialize trait for the structs, or else it looks overwhelming

I looked over on crates.io there are crates for open telemetry but, none provide the ability to serialize into the structs.

[nikhilsinhaparseable]

I also found some crates for otel but are vrl specific used by vector

[Eshanatnight]

https://crates.io/crates/opentelemetry
https://crates.io/crates/opentelemetry-otlp
https://crates.io/crates/opentelemetry-spanprocessor-any
https://crates.io/crates/opentelemetry_sdk
https://crates.io/crates/opentelemetry-contrib

There are more crates
They define the data structures and functions that we won't need to maintain. I think it's worth checking it out.

[nitisht]

closing in favour of #657