Cleanup/standardize pulsar.sh

[Spiker985]

• Removes release channels as they are no longer in use
• Standardize conditions, and add additional checks
  • Should fix the expr: syntax error: missing argument after ‘8’ error found in Various Errors and/or Non-Launch Depending on Launch Method #174

[confused-Techie]

While I can't test these changes, it looks good here, and there's no obvious failures on the test, but I don't believe the tests are checking this file at all to be honest.

But it looks good, and has clear and understandable code, so I'd say lets merge this one.

Although I did add a quality of life suggestion, which isn't required for a merge, but thought it to be helpful

[confused-Techie]

Thanks for adding the changes requested, if this looks fine to everyone in @pulsar-edit/core then I'll go ahead and merge in a little bit here