Refactor CLI args processing

[3flex]

The only functional change is that directories passed to detekt CLI are validated as directories. Other than that, this just makes the code a bit more consistent by using more of JCommander's features, and using stronger typing when args are processed.

[cortinico]

Mostly nits

[cortinico]

Q: moving from String? to List<Path> makes an empty input valid? Should we check inside PathValidator that the input is not empty?

[3flex]

If input is empty JCommander returns an error.

java -jar detekt-generator-1.23.6-all.jar -c . -d . -i returns ParameterException: Expected a value after parameter -i.

Any other value is validated to check that the paths exist. The only way to pass an empty list is to pass only a separator like -i , or -i ; but I don't think it's worth guarding against this.

[detekt-ci]

	Warnings
⚠️	This PR is approved with no milestone set. If merged, it won't appear in the detekt release notes.

Generated by 🚫 dangerJS against 578ef51

[codecov]

Codecov Report

Attention: Patch coverage is 89.65517% with 3 lines in your changes are missing coverage. Please review.

Project coverage is 83.72%. Comparing base (c3ff741) to head (578ef51).
Report is 4 commits behind head on main.

Files	Patch %	Lines
...itlab/arturbosch/detekt/generator/GeneratorArgs.kt	80.00%	0 Missing and 2 partials ⚠️
...gitlab/arturbosch/detekt/cli/ArgumentConverters.kt	90.00%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##               main    #7092      +/-   ##
============================================
+ Coverage     83.67%   83.72%   +0.05%     
+ Complexity     3957     3951       -6     
============================================
  Files           578      578              
  Lines         12164    12147      -17     
  Branches       2514     2502      -12     
============================================
- Hits          10178    10170       -8     
+ Misses          731      730       -1     
+ Partials       1255     1247       -8     

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[BraisGabin]

This PR also have another functional change that I think is good but just to point it out. When passing the inputs we allowed things like this "src/main , foo" and we map that to src/mainandfoo. Now we map it to src/main and foo`.

Also the new exception doesn't allow to spot those errors easily because the path doesn't quote the path so it is really difficult to spot that space. I'm going to create a new PR to fix this last point.

[BraisGabin]

Also we should use the splitter on the --includes and --excludes too. But I would like to first merge #7007 to avoid more conflicts.