Use JetBrains cache-redirector

[adam-enko]

Use JetBrains cache-redirector in Dokka build, Gradle integration tests, and Maven integration tests.

Update the Gradle Wrapper task to use the cache-redirector too, and add an explanation.

Part of KT-64200

[whyoleg]

LGTM, would be nice to leave a small comment on how to update Gradle wrapper now

[whyoleg]

just to clarify: after PR merged to update the version of Gradle, we need:

1. set gradleVersion to the new value
2. go to https://gradle.org/release-checksums/ and copy the checksum
3. set distributionSha256Sum to the new value
4. run gradle wrapper

correct?

Previously it was just gradle wrapper --gradle-version=8.8

[adam-enko]

Good point, I will double check and document the steps. Normally I update gradle.properties but yes, there are multiple ways.

Previously it was just gradle wrapper --gradle-version=8.8

And then re-run gradle wrapper, otherwise the wrapper scripts won't be updated 🙃

[adam-enko]

TIL how to update Gradle (while using distributionSha256Sum). It is not simple :(

Hopefully the instructions are clear - WDYT?

[adam-enko]

LGTM, would be nice to leave a small comment on how to update Gradle wrapper now

Very good idea, I will do that.