upgrade gradle wrapper from 8.1.1 to 8.10.1 in order to build with Java 22

[chrisrueger]

Based on a discussion in #6271 @reckart needed to upgrade gradle wrapper in order to build with Java 22.
Basically what was done is documented here: https://github.com/bndtools/bnd/blob/master/CONTRIBUTING.md#gradle-wrapper

This is an attempt to do so.
https://docs.gradle.org/8.10.1/release-notes.html

@pkriens I am unsure about the addition in TestHelper.groovy. Is this correct? Not sure what the intention of that method is.

[chrisrueger]

Just noticed this deprecation warning in the log of Validate Gradle Wrapper action

Warning: This job uses deprecated functionality from the 'gradle/wrapper-validation-action' action. Consult the logs for more details.
DEPRECATION: The action gradle/wrapper-validation-action has been replaced by gradle/actions/wrapper-validation. See https://github.com/gradle/actions/blob/main/docs/deprecation-upgrade-guide.md#the-action-gradlewrapper-validation-action-has-been-replaced-by-gradleactionswrapper-validation

I will look into this later

[chrisrueger]

@pkriens imo this can be merged. The deprecated GitHub action can be done separately.

[pkriens]

I am gonna trust you :-)