Add JDK 25 compatibility to functional tests

[dantte-lp]

Summary

Adds graceful handling for JDK 25 in functional tests. No production code changes.

Changes

File	Change	Why
PitestPluginPitVersionFunctionalSpec	Filter PIT < 1.19.0 on JDK 25+	ASM 9.7.1 doesn't support class file version 69 (safety net)
PitestPluginGradleVersionFunctionalSpec	Add VERSION_25 → 9.4.1 to compat map	Per Gradle compatibility matrix

Backward compatibility

All changes are conditional on JavaVersion >= 25 — no impact when running on JDK 17/21/24 (current CI matrix).

Test results

JDK 17: ./gradlew clean check funcTest → BUILD SUCCESSFUL
JDK 21: ./gradlew clean check funcTest → BUILD SUCCESSFUL

Notes

The @IgnoreIf for historyInputLocation on JDK 25 was removed after standalone testing confirmed PIT 1.22.1 (ASM 9.9.1) works correctly with history files on JDK 25 + class file version 69.

[dantte-lp]

Removed the @IgnoreIf for historyInputLocation — pushed 92b2f40.

Investigation results:

I ran standalone tests on Gradle 9.4.1 / GraalVM JDK 25.0.2 to check whether PIT actually crashes with historyInputLocation on JDK 25:

PIT	sourceCompatibility	Class version	historyInput	Result
1.22.1	17	61	yes	PASS
1.22.1	25	69	yes	PASS
1.22.1	25	69	no	PASS
1.18.0	17	61	no	PASS

PIT 1.22.1 (ASM 9.9.1) works correctly with historyInputLocation on JDK 25, even with class file version 69. The original @IgnoreIf was based on an incorrect assumption about ASM compatibility.

The remaining changes in this PR (PIT version filter for JDK 25+ and the Gradle version compatibility map entry) are still valid as safety nets for older PIT versions.

Full QA investigation: https://gist.github.com/dantte-lp/17c4e0aa3f5f84d6831cb12ceed9853b

[szpak]

TBH, I don't know how you/agent was able to test it in isolation. I spent some time today tweaking the configuration (and tests) for Gradle 9.1.0 compatibility (which is required for JDK 25 - #401).

[szpak]

Btw, even there I have some failing tests with JDK 25, but it is late, so @dantte-lp, I you would like to work on that branch to make all green with JDK 25, it would be great :-).

[szpak]

so @dantte-lp, I you would like to work on that branch to make all green with JDK 25, it would be great :-).

Just a moment after I sent it, I realized you already "fixed" one test in this MR and I fixed also the rest... Sorry for noise.

[szpak]

Let's close it in favor of (derived from that one) #401 which (in addition) effectively allows to run Gradle with JDK 25 (although this one ha nicer summary ;-) ).