Exit codes review

[JanKrivanek]

Problem

Review and adjust exit codes from New3CommandResult #3186

Options:

• We probably want to move away from HResults - but just for sure, added as well proposals for what the proper HResults could be.
• Added as well proposals for unix style exit codes (0-255)
• Alternatively we can exit with 0 (success) / 1 (error) - as it seems to be done by quite a few of our CLI tools (e.g. MSBuild exit code)

@baronfel - your insight and thoughts would be very appreciated here

Solution

Proposed what HResult or Unix compatible exit codes can be used for particular states - no actual code change yet Mostly collecting feedback now

Checks:

• Added unit tests
• Added #nullable enable to all the modified files ?

[JanKrivanek]

Superseded by #4787