chore: use consistent copyright header in .rs files

[xtqqczze]

No description provided.

[github-actions]

GNU testsuite comparison:

Skipping an intermittent issue tests/tail/follow-name (passes in this run but fails in the 'main' branch)
Congrats! The gnu test tests/date/date-locale-hour is no longer failing!
Note: The gnu test tests/basenc/bounded-memory is now being skipped but was previously passing.

[sylvestre]

ok when the ci is green, thanks!

[oech3]

Those headers are too big. Can we reduce size ot use small ref at least for?

[xtqqczze]

Yeah, the current headers are quite verbose, but for now these changes introduce consistency.

[github-actions]

GNU testsuite comparison:

Skip an intermittent issue tests/pr/bounded-memory (fails in this run but passes in the 'main' branch)
Note: The gnu test tests/tail/tail-n0f is now being skipped but was previously passing.

[sylvestre]

thanks!