This will output a warning if an invalid value is requested. The goal is to avoid
implicit conversion which might result in a zero-int value.

By using an enum we have a central place to provide docs for the most
common actions/restrictions. Also consumers can pass in type-safe enum
values instead of potentially undocumented strings that might contain typos.

Also it is better documents is a value is supposed to be authorized using
KAuthorized::authorize or KAuthorized::authorizeAction, in the case of "shell_access"
this was mixed up from time to time.

Considering that we do not want the parameter for the methods to become too long
I have deliberately decided against using `enum class`. Also we don't have
and usecases for the binary operators in combination with the newly added enums.

Task: https://phabricator.kde.org/T11948

This will become especially useful when moving state data from the config file
to a dedicated state data file.

Task: https://phabricator.kde.org/T12549

Otherwise we force consumers to use the config location for state data,
which is what we are trying to avoid.

Task: https://phabricator.kde.org/T12549

clang-tidy checks:
readability-isolate-declaration and readability-braces-around-statements

KF task: https://phabricator.kde.org/T14729

GIT_SILENT

This is the case where we expected to see Key[$d] in the config file,
and it was somehow broken. When saving, the key was omitted, so when
reloading the kdeglobals key was present again.

Detected when trying to write a unittest for a different patch...

I had to reshuffle the unittest a bit because testThreads calls
testSimple which didn't expect that the "[AAA]" group would actually
be deleted now.

GIT_SILENT

No impact on the rest of the test, but I was wondering if it might
break anything, better restore it just in case.

NO_CHANGELOG