Support configuration cache fully & Gradle 9 compatibility

[Vampire]

• I have read the guidelines for submitting issues

⚠️ Is your feature request related to a problem? Please describe

The plugin is not compatible with Gradle 9.
For example it accesses Task#project at execution time, which was deprecated and will fail with Gradle 9.

Maybe in the course of fixing this, supporting the configuration cache could also be reconsidered as it is one of the issues which makes the tasks incompatible right now.
The argument "isn't worth caching as it changes the versions file and thus invalidates the cache" is only true if it actually changes the file. If you use it to check for updates and no updates are available, the CC could be reused. :-)
And finally, since Gradle 8.1 the CC was promoted to stable.

💡 Describe the solution you'd like

Plugin compatible with Gradle 9 and optimally configuration cache

🤚 Do you want to develop this feature yourself?

• Yes
• No

[LouisCAD]

Configuration cache support was fully implemented for the refreshVersions task.
It's in the latest snapshot and will make it into a release next week.

Besides other tasks that are not supporting configuration cache yet, please let me know if you spot any other Gradle 9 compatibility issues.