Various changes to observer methods to align them with spec expectations

[manovotn]

Related to #28558

• All OM now implement getReception() method correctly (before we just returned Reception.ALWAYS)
• All OM now implement getDeclaringBean() through default method
• We now support notify(T event) via default impl - there are TCKs asserting you can manually invoke the method on OM

[gsmet]

I rebased on top of latest main due to some CI weirdness.

[Ladicek]

Otherwise LGTM.

[quarkus-bot]

Failing Jobs - Building 1361239

Status	Name	Step	Failures	Logs	Raw logs
✔️	JVM Tests - JDK 11
✖	JVM Tests - JDK 11 Windows	Build	Failures	Logs	Raw logs
✔️	JVM Tests - JDK 17
✔️	JVM Tests - JDK 18
✔️	Maven Tests - JDK 11
⌛	Maven Tests - JDK 11 Windows	Build	⚠️ Check →	Logs	Raw logs

Full information is available in the Build summary check run.

Failures

⚙️ JVM Tests - JDK 11 Windows #

- Failing: integration-tests/mongodb-rest-data-panache 

📦 integration-tests/mongodb-rest-data-panache

✖ io.quarkus.it.mongodb.rest.data.panache.MongoDbRestDataPanacheTest.shouldNotCreateOrDeleteAuthor - More details - Source on GitHub

java.lang.RuntimeException: 
java.lang.RuntimeException: io.quarkus.builder.BuildException: Build failure: Build failed due to errors
	[error]: Build step io.quarkus.mongodb.deployment.DevServicesMongoProcessor#startMongo threw an exception: java.lang.RuntimeException: java.lang.IllegalStateException: Previous attempts to find a Docker environment failed. Will not retry. Please see logs and check configuration

[manovotn]

CI failures are unrelated