Ban only unavailable config services when initializing config in CodeGenerator

[aloubyansky]

This change bans only those config services that are actually unavailable instead of assuming every service configured in the application module will not be available.
There are a couple of use-cases where this change could help:

1. if the class of a service impl configured in the application module is actually in a different module/jar and is available even in a phase before compile;
2. in other use-cases than generate-code, if the config initialization is called after the compile phase, the config service impl will be compiled and available by that time.

[quarkus-bot]

Failing Jobs - Building 5640250

Status	Name	Step	Failures	Logs	Raw logs
✖	Gradle Tests - JDK 11	Build	Failures	Logs	Raw logs
✔️	Gradle Tests - JDK 11 Windows
✔️	JVM Tests - JDK 11
✔️	JVM Tests - JDK 17
✖	JVM Tests - JDK 17 Windows	Build	Failures	Logs	Raw logs
✔️	JVM Tests - JDK 19

Full information is available in the Build summary check run.

Failures

⚙️ Gradle Tests - JDK 11 #

- Failing: integration-tests/gradle 

📦 integration-tests/gradle

✖ io.quarkus.gradle.builder.QuarkusModelBuilderTest.shouldLoadMultiModuleTestModel line 66 - More details - Source on GitHub

org.gradle.tooling.BuildException: Could not run build action using connection to Gradle distribution 'https://services.gradle.org/distributions/gradle-8.1.1-bin.zip'.
	at org.gradle.tooling.internal.consumer.ExceptionTransformer.transform(ExceptionTransformer.java:51)
	at org.gradle.tooling.internal.consumer.ExceptionTransformer.transform(ExceptionTransformer.java:29)

✖ io.quarkus.gradle.builder.QuarkusModelBuilderTest.shouldLoadMultiModuleDevModel line 100 - More details - Source on GitHub

org.gradle.tooling.BuildException: Could not run build action using connection to Gradle distribution 'https://services.gradle.org/distributions/gradle-8.1.1-bin.zip'.
	at org.gradle.tooling.internal.consumer.ExceptionTransformer.transform(ExceptionTransformer.java:51)
	at org.gradle.tooling.internal.consumer.ExceptionTransformer.transform(ExceptionTransformer.java:29)

---

⚙️ JVM Tests - JDK 17 Windows #

- Failing: extensions/scheduler/deployment 
! Skipped: extensions/quartz/deployment extensions/spring-scheduled/deployment integration-tests/devmode and 4 more

📦 extensions/scheduler/deployment

✖ io.quarkus.scheduler.test.PausedSchedulerTest.testSchedulerPauseResume line 47 - More details - Source on GitHub

org.opentest4j.AssertionFailedError: expected: <false> but was: <true>
	at org.junit.jupiter.api.AssertionFailureBuilder.build(AssertionFailureBuilder.java:151)
	at org.junit.jupiter.api.AssertionFailureBuilder.buildAndThrow(AssertionFailureBuilder.java:132)