Group together shell error strings

[FeralChild64]

String-related cleanup:

• grouped all the 'generic' shell strings - this way they will be easier to find when developing command/program
• made their IDs uniform
• dropped one string from MOUSECTL, add newline at the end of its error messages
• fixed one mistake in Polish translation

No action from translators should be necessary.

[kcgen]

Excellent systematic cleanup, @FeralChild64 !

All looks good from my side.

[johnnovak]

Nice cleanup job @FeralChild64 👍🏻

[kcgen]

Another big clean up -- nice, @FeralChild64 !

@MeAreJeenius , this touches some of Shell and its translation messages (but not Shell Batch); fingers crossed your branch rebases clean once this lands in main.