KRPC-585: Define BSR in Gradle plugin

[eminasljivic]

Subsystem
Gradle Plugin, Buf

Problem Description
KRPC-585 & #694: Currently there is no possibility to define BSR modules so that they can be imported in a proto files.

Solution
Add buf.deps property with .module(<module_name>) and lockFile. If modules were defined then the new task BufLockTask will run and either generate a buf.lock file with buf dep update or copy the provided lock file.

In addition instead of using workingDir as an input the three generated files buf.yaml, buf.gen.yaml and buf.lock are now marked as input. This is due to the fact that buf dep update generates files in the directory and would cause the BufGenerateTask to run every time even though the relevant files didn't change.

[Mr3zee]

Hey, nice work!

Two things I notice before I do an actual review:

• Please add free BSR account token to the CI, otherwise we might run out of free no account quota
• I see that you can't add deps per source set. Please address that and add comprehensive tests (deps should be transitive between source sets, additive in android variants case)