feat: Add option to control verbosity of `write_source_files`.

[r0bobo]

This adds a verbosity option to write_source_files that makes it possible to control what the output message looks like when running the targets that copies the files to the source tree. It has the options full which is the same as the current one and the default value, short which is a shorter version and quiet which doesn't output anything at all.

I don't have access to a Windows system, so the solution is not tested on Windows.

~When updating the docs I have a bigger diff than I expect to just as I explained in https://github.com/bazel-contrib/bazel-lib/pull/1032#issue-2794711472.~