Add missing Gradle UP-TO-DATE check annotations to support Gradle 7

[AndreasTu]

Since Gradle 7 Tasks with getters/properties throw errors if they are not properly annotated.

This fixes gatling/gatling/issues/4068

[Isammoc]

Thanks for this PR! ❤️
Can you add the corresponding tests (ensure that gradle 7 executes correctly).

I guess that should be there GradleCompatibilitySpec.groovy#L36
But I didn't check if other places need to be added.

[slandelle]

Also, once everything is fixed, could you please sign our CLA?

[AndreasTu]

@Isammoc I have added Gradle 7 to the test list.
@slandelle signed

Thanks for the fast feedback!

[Isammoc]

This modification will be part of our next release, when gatling 3.5.2 will be out. (This plugin version currently aligns with the gatling version)

[jonatan-ivanov]

@Isammoc Do you happen to have any ETA for 3.5.2? I'm asking because the issue blocks users of the plugins in two things:

1. Upgrading to Gradle 7.0
2. Upgrading to Java 16 (Gradle 6.x does not support Java 16 so users need to upgrade to 7.0)

[slandelle]

No ETA yet. There are some HTTP/2 issues we want to fix first. Within 1 month max.

[jonatan-ivanov]

@slandelle Do you happen to have any ETA for releasing this fix so that users can use Java 16 and Gradle 7.0?

[slandelle]

The week after next week.