Bump Gradle to 8.6

[theqeeqez]

Bump Gradle to 8.6 and Get rid of Deprecation messages

What is done:

1. Run ./gradlew wrapper --gradle-version=8.6 to switch to the new gradle
2. Run ./gradlew build --warning-mode all to check all the deprecations we have
3. Bump minor versions
   • org.jfrog.buildinfo:build-info-extractor-gradle from 5.1.10 to 5.1.14
   • org.junit:junit-bom from 5.10.1 to 5.10.2

Fixed Deprecations:

1. .getBuildDir() now .getLayout().getBuildDirectory().getAsFile().get() in SpringPublishLocalPlugin.java
2. Bump dependencies. Older versions use deprecated gradle features
   • io.github.gradle-nexus:publish-plugin from 1.3.0 to 2.0.0-rc-2
   • spring-javaformat-gradle-plugin from 0.0.39 to 0.0.41
3. JUnit initialization should be similar to gradle docs, otherwise gradle shows deprecation message (message appears time to time)

[sjohnr]

Thanks @qeeqez! This is now merged to main as c526b3b along with polish commit 4e8587c.