pass-secret-service: various improvements

Allow setting the application package and storePath used by the
config. Since the `programs.password-store` Home Manager module sets
config values via global environment variables, the default behavior
of the module should continue to behave as before for the user.

Additionally,

- Adds a few tests.

- Use "escapeShellArg" function call to the path parameter call to
  ensure paths with spaces work.

- Allow not setting storePath, which will cause `pass_secret_service`
  to default to using `~/.password-store`.

- If `pass-secret-service` is enabled, set its store path to default
  to the one defined in our password-store environment settings.

- Add myself (houstdav000) as maintainer.

tests/default.nix

@@ -189,6 +189,7 @@ import nmt {
     ./modules/services/mpdris2
     ./modules/services/pantalaimon
     ./modules/services/parcellite
+    ./modules/services/pass-secret-service
     ./modules/services/pbgopy
     ./modules/services/picom
     ./modules/services/playerctld