[DOCS] Add OpenTelemetry and Jaeger event intake API to OpenAPI document

[lcawl]

Relates to https://github.com/elastic/apm-server/issues/12903

This PR updates the OpenAPI specification to include details from https://www.elastic.co/guide/en/observability/current/apm-api-otlp.html and https://www.elastic.co/guide/en/observability/current/apm-api-jaeger.html

There were no details about the type of request and response received from these APIs, so I've left them generic for now.

NOTE: I've also used the "redocly split" command to split out the source files for the OpenAPI components and paths,etc. so that they can be used to also generate documents for the Serverless APIs

[mergify[bot]]

This pull request does not have a backport label. Could you fix it @lcawl? 🙏 To fixup this pull request, you need to add the backport labels for the needed branches, such as:

• backport-7.17 is the label to automatically backport to the 7.17 branch.
• backport-8./d is the label to automatically backport to the 8./d branch. /d is the digit.

NOTE: backport-skip has been added to this pull request.

[lcawl]

@simitt I've added deprecated: true to the Jaeger operations but if you prefer that I remove those paths entirely, I can do that instead.

[simitt]

@elastic/obs-ds-intake-services please give this PR a review. @carsonip has https://github.com/elastic/apm-server/issues/11671 assigned for this iteration to deprecate Jaeger, this should align with this PR.