Update postgres_exporter from 0.17.1 to 0.20.0

[prometheus-rpm-bot]

https://github.com/prometheus-community/postgres_exporter/releases/tag/v0.20.0
Release notes:

BREAKING CHANGES:

### Collector flag changes

The `replication_slot` collector has been renamed to `replication_slots`.
Users explicitly enabling or disabling this collector must update their flags:
* `--collector.replication_slot` -> `--collector.replication_slots`
* `--no-collector.replication_slot` -> `--no-collector.replication_slots`
The `--disable-settings-metrics` flag and
`PG_EXPORTER_DISABLE_SETTINGS_METRICS` environment variable have been removed.
Use `--no-collector.settings` instead.

### Metric name changes

The metrics previously exposed by the `replication_slot` collector have been
renamed to use the `pg_replication_slots_` prefix. Update alerts, recording
rules, and dashboards that reference these metrics:
* `pg_replication_slot_slot_current_wal_lsn` -> `pg_replication_slots_slot_current_wal_lsn`
* `pg_replication_slot_slot_confirmed_flush_lsn` -> `pg_replication_slots_slot_confirmed_flush_lsn`
* `pg_replication_slot_slot_is_active` -> `pg_replication_slots_slot_is_active`
* `pg_replication_slot_safe_wal_size_bytes` -> `pg_replication_slots_safe_wal_size_bytes`
* `pg_replication_slot_wal_status` -> `pg_replication_slots_wal_status`

### Standalone collector behavior

The `settings`, `stat_activity`, `stat_archiver`, `stat_replication`, and
`replication_slots` metrics now come from standalone collectors instead of the
legacy default metric map.
These metrics no longer honor `--metric-prefix`, no longer include deprecated
`constantLabels`, and are no longer disabled by `--disable-default-metrics`.
To stop collecting them, disable the corresponding collector explicitly with
its `--no-collector.*` flag.

* [CHANGE] Move `pg_settings` metrics to the standalone `settings` collector by @ArthurSens in https://github.com/prometheus-community/postgres_exporter/pull/1303
* [CHANGE] Move `stat_archiver` metrics to a standalone collector by @ArthurSens in https://github.com/prometheus-community/postgres_exporter/pull/1304
* [CHANGE] Move `stat_activity` metrics to a standalone collector by @ArthurSens in https://github.com/prometheus-community/postgres_exporter/pull/1305
* [CHANGE] Move `stat_replication` metrics to a standalone collector by @ArthurSens in https://github.com/prometheus-community/postgres_exporter/pull/1306
* [CHANGE] Rename `replication_slot` to `replication_slots` and move replication slot metrics to a standalone collector by @ArthurSens in https://github.com/prometheus-community/postgres_exporter/pull/1307
* [ENHANCEMENT] Publish container images to GHCR and update PromCI release automation by @roidelapluie in https://github.com/prometheus-community/postgres_exporter/pull/1322
* [BUGFIX] Fix duplicate `pg_stat_progress_vacuum` metrics for cross-database vacuums by @steinbrueckri in https://github.com/prometheus-community/postgres_exporter/pull/1262
* [BUGFIX] Fix `pg_settings` collection when `short_desc` is NULL by @jun-gradial in https://github.com/prometheus-community/postgres_exporter/pull/1327