Add Java 18 to matrix of 'JVM Tests' CI job

[famod]

With the EA job now running with java 19-ea (#26374), it pobably makes sense to have some continuous coverage of Java 18.

Related to #24789

[quarkus-bot]

Failing Jobs - Building 583856b

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

Full information is available in the Build summary check run.

Failures

⚙️ JVM Tests - JDK 11 Windows #

- Failing: extensions/mongodb-client/deployment 
! Skipped: extensions/liquibase-mongodb/deployment extensions/panache/mongodb-panache-common/deployment extensions/panache/mongodb-panache-kotlin/deployment and 8 more

📦 extensions/mongodb-client/deployment

✖ io.quarkus.mongodb.NamedMongoClientConfigTest. - 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

✖ io.quarkus.mongodb.NamedReactiveMongoClientConfigTest. - 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

[famod]

@gsmet any objections?

[gsmet]

I'm a bit torn. I'm a bit worried that it will overload our CI. But we can try and see how it goes.

[famod]

If it does we could implement a nightly job instead, with more coverage. Similar to the EA job.
Could be a nice use case for GitHub reusable workflows.