Extract declarative config to new opentelemetry-sdk-extension-decelar…

[jack-berg]

Resolves #7292

Extract declarative config from opentelemetry-sdk-extension-incubator to opentelemetry-sdk-extension-declarative-config.

Root package at io.opentelemetry.sdk.declarativeconfig.

Other options considered:

• opentelemetry-sdk-config - I.e. make declarative config a peer of opentelemetry-sdk-{signal}. The existence of SdkConfigProvider - which currently resides in opentelemetry-sdk-all suggests this should be the case. However, declarative config requires dependencies on each of the other opentelemetry-sdk-{signal} modules, and has a YAML dependency which we'll want to keep opt in.
• opentelemetry-sdk-extension-autoconfigure - I.e. extend existing autoconfigure with declarative config. I don't hate this idea, but it would mean adding a YAML dependency to autoconfigure. As it stands currently and with this PR, autoconfigure has a compileOnly dependency on declarative config where the behavior changes at runtime if available, i.e. we start looking for OTEL_CONFIG_FILE being set and if so delegating config to declarative config.

Coming in a followup PRs:

• Commit schema generated POJOs to version control. Now that declarative config is stable, we should work towards adding the POJOs corresponding to stable types to our stable API. This will allow users to reliably build / customize the in-memory representation of the data model.
• Consider making YAML parsing pluggable. Right now we use org.snakeyaml:snakeyaml-engine for parse input YAML string to Object, then we use jackson to convert Object to OpenTelemetryConfigurationModel. If org.snakeyaml.snakeyaml-engine had unsolved vulnerabilities or if breaking changes caused runtime errors from the diamond dependency problem, then users would have no recourse. We could make these functions pluggable via SPI and try to provide at least one other implementation.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 90.25%. Comparing base (ca41b47) to head (db30767).

Additional details and impacted files

@@            Coverage Diff            @@
##               main    #8265   +/-   ##
=========================================
  Coverage     90.25%   90.25%           
  Complexity     7683     7683           
=========================================
  Files           850      850           
  Lines         23190    23190           
  Branches       2353     2353           
=========================================
  Hits          20930    20930           
  Misses         1533     1533           
  Partials        727      727           

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[robsunday]

Looks good with some minor comments

[zeitlinger]

Root package is io.opentelemetry.sdk.declarativeconfig - not io.opentelemetry.sdk.declarative.config as pr body says.

I do want to try out the opentelemetry-sdk-extension-autoconfigure alternative in a different PR. Will link here when done.

[zeitlinger]

I do want to try out the opentelemetry-sdk-extension-autoconfigure alternative in a different PR. Will link here when done.

Here it is: #8270

That new PR has the advantage that it keeps the yaml deps optional.