Avoid duplicate types between Maui and Maui Graphics

[jsuarezruiz]

Use the .NET MAUI types for LineCap, LineJoin, TextAlignment, etc. to avoid duplicates.

[jonlipsky]

@jsuarezruiz We should talk about this PR. Here are my quick thoughts:

1. I'm fine with the changes recording the enums to match Maui.Core.
2. I like the name FontSlant. Simpler than what we're currently using.
3. It's minor, but I don't like the "Pen" prefix on the LineJoin and LineCap enums. There is already a prefix "Line" on those enums that designate what it's for.
4. Personally, I think HorizontalAlignment and VerticalAlignment should be separate enums. "Justified" doesn't apply to both of them. I don't like having ambiguous values in the library.

[serdarb]

I didn't read all the code carefully.
But I wanted to say, you better keep HorizontalAlignment and VerticalAlignment
because it is instinctively understood the other suggestion is not.