Manage pgbouncer configuration from compute_ctl:

- add pgbouncer_settings section to compute spec;
- add pgbouncer-connstr option to compute_ctl.
- add pgbouncer-ini-path option to compute_ctl. Default: /etc/pgbouncer/pgbouncer.ini

Apply pgbouncer config on compute start and respec to override default spec.

Save pgbouncer config updates to pgbouncer.ini to preserve them across pgbouncer restarts.

deny.toml

@@ -35,6 +35,7 @@ allow = [
     "Artistic-2.0",
     "BSD-2-Clause",
     "BSD-3-Clause",
+    "CC0-1.0",
     "ISC",
     "MIT",
     "MPL-2.0",