feat: Allow the GUI to handle command-line args like the console application

[mwanchap]

• All arguments supported by the console application are now supported by the GUI. For example, to check some of the shorter System namespace directories in your GAC:
  PathLengthCheckerGUI.exe RootDirectory=C:\Windows\Microsoft.NET\ RootDirectoryReplacement=D:\ SearchOption=All TypesToInclude=OnlyDirectories SearchPattern=System.* MinLength=30 MaxLength=40 Output=All
• The GUI will also display the same argument usage text as the console application if incorrect arguments are provided.
• Still supports the root directory argument alone (e.g. via dropping a folder onto PathLengthCheckerGUI.exe as in PR feat: Enable providing root directory to GUI app via command-line or drag-and-drop #40) or via the newly-supported RootDirectory parameter. Using either results in the search running using defaults for everything else. For example:
  • Directory alone: PathLengthCheckerGUI.exe C:\path\to\root
  • RootDirectory parameter: PathLengthCheckerGUI.exe RootDirectory=C:\path\to\root
• Moved argument parsing and usage info text into ArgumentParser.cs to allow both to be used from either the console application or the GUI.
• Changed OutputType to a property of PathLengthSearchOptions (rather than just being a string in Program.cs) so the GUI can use it too.

[mwanchap]

Oh, I forgot to update the readme. I'll do that in my next PR ;)

[deadlydog]

Thanks for the PR. I'll try and review it in the next couple days 👍

[deadlydog]

Sorry, it's been a busy week and I was sick over the weekend, but this is still on my radar.

[deadlydog]

Looks good 👍Thanks for the PR :)

[deadlydog]

Oh, I forgot to update the readme. I'll do that in my next PR ;)

Hey @mwanchap just curious if you still planned to do this or not. If not, I don't mind doing it, but if you need another PR for hacktoberfest I'll leave it for you :)

[mwanchap]

Yep, just about to! Thanks for your patience, my wife and I just got back from our first real holiday since 2020 became deep-fried nonsense, and I'm still catching up on notifications and such...
Edit: Bah! I forgot that GitHub doesn't automagically squash commits in PRs like Azure Devops can. Apologies for cluttering up your master branch, I should have rebased this one.