test gm commands end to end

[amtoine]

related to

• test coverage #24

description

in order to be able to test the gm remove command:

• add --no-confirm to gm remove

in a new tests/gm.nu test module, adds

• a run-with-env command to take care of the test environment wrapping and cleaning
• tests for
  • gm list
  • gm update-cache
  • gm status
  • gm clone
  • gm remove
• the true expected errors next to assert error in NOTE, for when we'll be able to check the content of an error in Nushell 😏