Don't use ember-cli project instance outside of ember-cli commands

[bertdeblock]

Part of decoupling ember-try from ember-cli.

This way, only the code in lib/commands is coupled to ember-cli.
The next step would be to move the run portion of the commands to separate files.
This would allow us to move everything to ES modules, except the commands.
The commands can async import and run the ES modules.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 95.10%. Comparing base (d3b56f1) to head (f747ca7).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1036      +/-   ##
==========================================
- Coverage   95.49%   95.10%   -0.40%     
==========================================
  Files          21       21              
  Lines         511      511              
==========================================
- Hits          488      486       -2     
- Misses         23       25       +2     

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[bertdeblock]

Still need to update getting the config without a project instance.