Replace sudo param with maybe_sudo method.

[theory]

The maybe_sudo method creates a new command based on whether sudo might be needed and, if so, whether pkglibdir is writable. If sudo is true and pkglibdir is not writable it creates a Command with sudo as the program and the program passed as its first argument. Otherwise it returns a Command with the passed program.

With that intelligence, remove the sudo param from the interface and all methods. There will be no need to specify sudo as a boolean, as the package can figure it out for itself.

In the future it might be necessary to allow the user to specify a path to sudo (and make and cargo and whatever else?), but for now it will be enough to have the user make sure that such commands are in the path.

Also remove mut from PgConfig::get, as it's unnecessary and makes its usage more difficult. Found while using it in maybe_sudo.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 98.19%. Comparing base (8c20357) to head (ea8ff13).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #22      +/-   ##
==========================================
+ Coverage   98.18%   98.19%   +0.01%     
==========================================
  Files          10       10              
  Lines         495      499       +4     
==========================================
+ Hits          486      490       +4     
  Misses          9        9              

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.