woblerr/pgbackrest_exporter v0.18.0 on GitHub

Bump dependencies to fix Dependabot alert #82.
Allow passing of TLS certificates inline #83:
- Bump github.com/prometheus/exporter-toolkit from v0.9.1 to v0.11.0. The TLSCert, TLSKey and ClientCAs can be passed inline as a string as part of the TLSConfig.
- Bump github.com/prometheus/common from v0.45.0 to v0.54.0.
- Bump github.com/prometheus/client_golang from v1.14.0 to v1.19.1.
- Add test cases for e2e tests:
  - launch of the exporter specifying the configuration file for TLS (certificates inline) and without basic auth;
  - launch of the exporter specifying the configuration file for TLS and client certificate (any cert);
  - launch of the exporter specifying the configuration file for TLS and client certificate (signed cert).
Bump default pgBackRest version in container to v2.53 #84 #85 #87.
Add new backup references metrics #88:
- pgbackrest_backup_references;
- pgbackrest_backup_last_references.
Add new flag --backrest.reference-count.