[LOCAL] Set kotlin.jvm.target.validation.mode=warning on user projects

[cortinico]

Summary:

This is a fix for reactwg/react-native-releases#54 (comment)
It sets kotlin.jvm.target.validation.mode=warning so that projects won't break if they're using Kotlin 1.8+ and have JDK versions misaligned due to external libraries.

This doens't need to be backported to main as on main we set jvmToolchain(11) for all the libraries so this flag is unnecessary.

Also this is not a .0 blocker and can land in .1

Also this requires a bump of RNGP

Changelog:

[INTERNAL] - Set kotlin.jvm.target.validation.mode=warning on user projects

Test Plan:

Tested locally with ./gradlew build.

[cortinico]

@kelset has this been reverted (#37885) and the release branch force-pushed?

[kelset]

@cortinico yes - we had to clean up the branch ahead of 0.72.0. I'll take care of manually reapplying in the branch once we start working on 0.72.1

[cortinico]

@cortinico yes - we had to clean up the branch ahead of 0.72.0. I'll take care of manually reapplying in the branch once we start working on 0.72.1

In the future, I would suggest we avoid to force push on release branches (we can add a branch protection against force push, for security reasons also) and instead just add a revert commit.