[API] Introduce a new global level api.diag for internal Diagnostic Logging (Part 1)

[MSNev]

Introduction of new api.diag global logger as discussed during SIG meetings and linked to #1754

Basic outline

• Provide a top-level diagnostic logger from the API as api.diag with methods like api.diag.warn, api.diag.debug, etc.
• diag logger is no-op by default
• register a default logging implementation by calling api.diag.setLogger(loggingImpl)

Part 1

• For now we should keep but deprecate direct use of the NoopLogger and ConsoleLogger classes

Part 2

Will include breaking changes

• Once contrib is changed to use api.diag, these exports will be removed, this will require that they stop using local Logger instances
• This will also have breaking changes for
  • Configuration definitions that use api.Logger and core.LogLevel
  • Functions that currently get or pass api.Logger instances
  • The type of the environment OTEL_LOG_LEVEL

[MSNev]

Please assign to me as I can't assign it myself

[vmarchaud]

Quick question: does the exact name has been discussed in the SIG today (i couldn't attend sadly), i feel like shortening to diag kinda "obsfucate" its usage, what about just using api.diagnostics ?

[MSNev]

It was originally discussed 2 Sig's back, and part of the reason for the shortened name is to better support code minification, which is also the reason for introducing in the first place see #1754 for part of the discussion

[vmarchaud]

Okay cool i didn't miss anything then. I understand the code minification issue that of course impact everyone using otel, however i want to be sure that we all agree on "sacrificing" readability (at least in my opinion) for this goal.