[PROPOSAL] psql tab completion: support ALTER ROLE ... IN DATABASE ... RESET

Hi hackers,

I'd like to work on a small psql tab-completion improvement.

Problem:
psql currently has a missing completion path for:
ALTER ROLE <role> IN DATABASE <db> RESET ...

There is an in-code TODO marker for this case in src/bin/psql/tab-complete.in.c.

Proposal:
- Add completion support after "... IN DATABASE <db> RESET"
- Reuse existing completion behavior/style used by ALTER ROLE ... RESET
- Add regression coverage in src/bin/psql/t/010_tab_completion.pl

Non-goals:
- No backend behavior changes
- No SQL grammar changes

If this direction looks good, I can send a patch.

Thanks,
xianbinzhu