fixes #2585: Make spotlessInstallGitPrePushHook task compatible with Gradle configuration cache

[jsoberg]

Overview

As described in #2585, the spotlessInstallGitPrePushHook task will currently fail when configuration cache is enabled because it attempts to reference the Project during execution time. This PR moves the Project reference (for grabbing root dir) before execution time, following the pattern that SpotlessDiagnoseTask and other tasks use.

Testing

Ran unit tests, and verified before/after by running the task in https://github.com/meshtastic/Meshtastic-Android with local maven install (failed to run before, succeeded afterward).

PR Follow-ups

After creating the PR, please add a commit that adds a bullet-point under the [Unreleased] section of CHANGES.md, plugin-gradle/CHANGES.md, and plugin-maven/CHANGES.md which includes:

• a summary of the change
• either
  • a link to the issue you are resolving (for small changes)
  • a link to the PR you just created (for big changes likely to have discussion)

If your change only affects a build plugin, and not the lib, then you only need to update the plugin-foo/CHANGES.md for that plugin.

If your change affects lib in an end-user-visible way (fixing a bug, updating a version) then you need to update CHANGES.md for both the lib and all build plugins. Users of a build plugin shouldn't have to refer to lib to see changes that affect them.

This makes it easier for the maintainers to quickly release your changes :)

[jsoberg]

Updated changefiles as requested ✔️ lmk if I should be adding anything else, happy to update