Align log sdk naming with api

[jack-berg]

Resolves #2752.

This aligns log SDK and API concepts which have diverged after the merged of #2676. This PR brings alignment to the log API and SDK, and in brings the log signal into alignment with tracing and metrics where there is conceptual overlap. There shouldn't be any new concepts introduced here.

• Rename ../logs/logging-library-sdk.md to ../logs/sdk.md
• Remove wording from SDK that implies that an API doesn't exist, like this.
• Move How to Create Log4j Style Appender to api.md since it describes an API use case.
• Move Implicit / Explicit Context Injection sections to api.md since they describe API level considerations.
• Rename Logger create method to be emit, to align with SDK concept of LogRecordProcessor#onEmit(..).
• Rename LogProcessor, LogExporter to LogRecordProcessor, LogRecordExporter.
• Fill in various SDK level TODOs related to shutdown and flushing. The language from these was taken directly from the metrics / tracing SDK - no new concepts were introduced.

[tigrannajaryan]

Thanks for working on this!

[tigrannajaryan]

I will keep this open for a bit to allow time to review the last changes.

[CodeBlanch]

@jack-berg @scheler

Events require the event.domain attribute. The API MUST not allow creating an
Event if the Logger instance doesn't have event.domain scope attribute.

Can you clarify for me what to do in the case of missing event.domain to the EmitEvent call? Is it a no-op or a throw? Do I generate a log to alert the user?

Also, is it valid if name is passed as null or empty?

[scheler]

@CodeBlanch both domain and name are required for an Event and also cannot be empty or null. So EmitEvent call should throw an error if event.domain attribute is missing or is null/empty. Same with name - if it is null or empty, EmitEvent should return failure or throw an error.