Declare Gradle inputs to tasks for rewrite-csharp and rewrite-python

[greg-at-moderne]

What's changed?

Gradle build re-configuration. Declaring Gradle-level inputs for testRuntimeClasspath and runtimeClasspath in rewrite-csharp, rewrite-python. Currently none are declared.

What's your motivation?

An attempt to fix no caching for some of the tasks.
E.g.
https://ge.openrewrite.org/s/5a46joy4lwmha/timeline?view=ungrouped - a scheduled CI run on main shows:

The task was not up-to-date because there was no task history available. 
Cache key	fd1c5fc0124617286fc9bd203e2fdc49
Not cacheable	Gradle would require more information to cache this task.