If the socketDir is in tmpfs, or if it is deleted by some other process, we would want the socketDir to be created, if not already present, on restarts.
* Use psql instead of postgres, as a result, use `pg_ctl` to temporarily start the postgres server in `${name}-init` process.
* Avoid creating a custom `postgresPkg` with extensions by using `apply` attribute provided by `mkOption`
* Refactor setup script, use `writeShellApplication` and resolve shell-check errors
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Co-authored-by: shivaraj-bh <sbh69840@gmail.com>
