[shipa-2799] - Starting process via Ketch CLI outputs "Successfully started!" when passing invalid process name

[kavinaravind]

Description

This addresses the following bug:

When passing invalid process name to app stop, correct output is shown (process not found) When passing invalid process name to app start the app does not start as expected, but the output shows “Successfully started!”

Fixes # (issue)

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Chore (documentation addition or typo, file relocation)

Testing

• New tests were added with this PR that prove my fix is effective or that my feature works (describe below this bullet)
• This change requires no testing (i.e. documentation update)

Documentation

• All added public packages, funcs, and types have been documented with doc comments
• I have commented my code, particularly in hard-to-understand areas

Final Checklist:

• I followed standard GitHub flow guidelines
• I have performed a self-review of my own code
• My changes generate no new warnings

Additional Information (omit if empty)

Please include anything else relevant to this PR that may be useful to know.

[stinkyfingers]

Looks good. I noticed that when it correctly fails to start, it says "failed to stop app." May want to change the string here too: https://github.com/theketchio/ketch/blob/main/cmd/ketch/app_start.go#L59