Add additional LineStyles

[Nutzzz]

Added dashed, dotted, and thick line styles and combinations where available.

Pull Request checklist:

• I've named my PR in the form of "Fixes #issue. Terse description."
• My code follows the style guidelines of Terminal.Gui - if you use Visual Studio, hit CTRL-K-D to automatically reformat your files before committing.
• My code follows the Terminal.Gui library design guidelines
• I ran dotnet test before commit
• I have made corresponding changes to the API documentation (using /// style comments)
• My changes generate no new warnings
• I have checked my code and corrected any poor grammar or misspellings
• I conducted basic QA to assure all features are working

[Nutzzz]

I added a few Unit Tests dealing with thick and thin combinations, but I'll make more for the dashed and dotted variations.

[tig]

This is fantastic!

Note that I'm knees deep in a massive refactoring of related border LineCanvas stuff right now that will greatly benefit from your work.

However, this also means I'm going to hold off reviewing and merging this pr until I'm done.

If you want, you can retarget this pr to be a pr to my pr (#2527) which may streamline things.

[tig]

Looking great. Big add.

See the bugs I think I found in my comments.

[BDisp]

Same as #2542 (comment). The LineCanvas is bad clipped.

[tig]

here's the fix:

		var borderBounds = new Rect (
				screenBounds.X + Math.Max (0, Thickness.Left - 1),
				screenBounds.Y + Math.Max (0, Thickness.Top - 1),
				screenBounds.Width - (Math.Max (0, Math.Max (0, Thickness.Left - 1) + Math.Max (0, Thickness.Right - 1))),
				screenBounds.Height - (Math.Max (0, Math.Max (0, Thickness.Top - 1) + Math.Max (0, Thickness.Bottom - 1))));

[BDisp]

here's the fix:

		var borderBounds = new Rect (
				screenBounds.X + Math.Max (0, Thickness.Left - 1),
				screenBounds.Y + Math.Max (0, Thickness.Top - 1),
				screenBounds.Width - (Math.Max (0, Math.Max (0, Thickness.Left - 1) + Math.Max (0, Thickness.Right - 1))),
				screenBounds.Height - (Math.Max (0, Math.Max (0, Thickness.Top - 1) + Math.Max (0, Thickness.Bottom - 1))));

Thanks @tig. That throws exceptions if dimensions are negative. This is more accurate:

			var borderBounds = new Rect (
				screenBounds.X + Math.Max (0, Thickness.Left - 1),
				screenBounds.Y + Math.Max (0, Thickness.Top - 1),
				Math.Max (0, screenBounds.Width - Math.Max (0, Math.Max (0, Thickness.Left - 1) + Math.Max (0, Thickness.Right - 1))),
				Math.Max (0, screenBounds.Height - Math.Max (0, Math.Max (0, Thickness.Top - 1) + Math.Max (0, Thickness.Bottom - 1))));

[Nutzzz]

FWIW, here were some experiments with one more dash type. Unfortunately, the trick I used to keep horizontal and vertical looking somewhat similar won't work without mixing two different glyphs for the horizontal line.

[tig]

here's the fix:

	var borderBounds = new Rect (

			screenBounds.X + Math.Max (0, Thickness.Left - 1),

			screenBounds.Y + Math.Max (0, Thickness.Top - 1),

			screenBounds.Width - (Math.Max (0, Math.Max (0, Thickness.Left - 1) + Math.Max (0, Thickness.Right - 1))),

			screenBounds.Height - (Math.Max (0, Math.Max (0, Thickness.Top - 1) + Math.Max (0, Thickness.Bottom - 1))));

Thanks @tig. That throws exceptions if dimensions are negative. This is more accurate:

			var borderBounds = new Rect (

				screenBounds.X + Math.Max (0, Thickness.Left - 1),

				screenBounds.Y + Math.Max (0, Thickness.Top - 1),

				Math.Max (0, screenBounds.Width - Math.Max (0, Math.Max (0, Thickness.Left - 1) + Math.Max (0, Thickness.Right - 1))),

				Math.Max (0, screenBounds.Height - Math.Max (0, Math.Max (0, Thickness.Top - 1) + Math.Max (0, Thickness.Bottom - 1))));

Thanks.

Reminder: all this is temporary. My dream is all these border/title things are eventually done via subviews of the Frame.

[tig]

@Nutzzz in case you didn't see this has merge conflicts.