Get annotation processing going with Eclipse Compiler for Java

[arouel]

Problem

I'm writing a HTTP feature for Helidon (related to #8897) and want to work with Eclipse IDE, but the Helidon annotation processors throw an exception because the Eclipse Compiler for Java (ECJ) behaves slightly different compared to javac.

Solution

Some changes were necessary to get the annotation processing going:

• Due to the implementation of IdeFilerImpl:236 there is no handling for javax.tools.StandardLocation.SOURCE_PATH implemented and therefore the search for module-info.java fails with a thrown IllegalArgumentException. Ignoring this exception when compiling with the ECJ is fine.
• There is also a case where the ECJ cannot resolve a type name and the Element parameter is null. Returning an empty Optional enables the caller to fall back.
• Due to the implementation of IdeInputFileObject:50 the deletion of a FileObject throws an IllegalStateException. Ignoring any exception when compiling with the ECJ should be fine.

I have successfully tested the changes suggested here in a current Eclipse IDE (Version: 2024-06 (4.32.0)) on my local computer.

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[tomas-langer]

If you want to go forward with this PR, kindly sign the OCA, as otherwise we cannot accept your contribution.

[arouel]

@tomas-langer I added one more commit to handle the last case I had issues with when using Eclipse IDE. Can you have a look at it as well? I signed the OCA already, I guess it needs a bit to be approved.

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