[DPE-4642] Multiple databases

[dragomirp]

Add support for wildcard databases

VM PRs implementing the same functionality:

• https://github.com/canonical/pgbouncer-operator/pull/210
• https://github.com/canonical/pgbouncer-operator/pull/228
• https://github.com/canonical/pgbouncer-operator/pull/251
• https://github.com/canonical/pgbouncer-operator/pull/257

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 80.59701% with 13 lines in your changes missing coverage. Please review.

Project coverage is 71.04%. Comparing base (96c62d1) to head (eaf4419).

Files	Patch %	Lines
src/charm.py	80.32%	7 Missing and 5 partials :warning:
src/relations/pgbouncer_provider.py	75.00%	0 Missing and 1 partial :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #324 +/- ## ========================================== + Coverage 70.63% 71.04% +0.40% ========================================== Files 8 8 Lines 1192 1250 +58 Branches 218 236 +18 ========================================== + Hits 842 888 +46 - Misses 268 275 +7 - Partials 82 87 +5 ```

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