Add support for the rectangular area operations

[j4james]

Summary of the Pull Request

This PR adds support for the rectangular area escape sequences:
DECCRA, DECFRA, DECERA, DECSERA, DECCARA, DECRARA, and
DECSACE. They provide VT applications with an efficient way to copy,
fill, erase, or change the attributes in a rectangular area of the
screen.

PR Checklist

• Closes Add support for the rectangular area operations #14112
• CLA signed.
• Tests added/passed
• Documentation updated.
• Schema updated.
• I've discussed this with core contributors already. Issue number
  where discussion took place: Add support for the rectangular area operations #14112

Detailed Description of the Pull Request / Additional comments

All of these operations take a rectangle, defined by four coordinates.
These need to have defaults applied, potentially need to be clipped
and/or clamped within the active margins, and finally converted to
absolute buffer coordinates. To avoid having to repeat that boilerplate
code everywhere, I've pulled that functionality out into a shared method
which they all use.

With that out of the way, operations like DECFRA (fill), DECERA
(erase), and DECSERA (selective erase) are fairly simple. They're just
filling the given rectangle using the existing methods _FillRect and
_SelectiveEraseRect. DECCRA (copy) is a little more work, because we
didn't have existing code for that in AdaptDispatch, but it's mostly
just cloned from the conhost _CopyRectangle function.

The DECCARA (change attributes) and DECRARA (reverse attributes)
operations are different though. Their coordinates can be interpreted as
either a rectangle, or a stream of character positions (determined by
the DECSACE escape sequence), and they both deal with attribute
manipulation of the target area. So again I've pulled out that common
functionality into some shared methods.

They both also take a list of SGR options which define the attribute
changes that they need to apply to the target area. To parse that data,
I've had to refactor the SGR decoder from the SetGraphicsRendition
method so it could be used with a given TextAttribute instance instead
of just modifying the active attributes.

The way that works in DECCARA, we apply the SGR options to two
TextAttribute instances - one with all rendition bits on, and one with
all off - producing a pair of bit masks. Then by ANDing the target
attributes with the first bit mask, and ORing them with the second, we
can efficiently achieve the same effect as if we'd applied each SGR
option to our target cells one by one.

In the case of DECRARA, we only need to create a single bit mask to
achieve the "reverse attribute" effect. That bit mask is applied to the
target cells with an XOR operation.

Validation Steps Performed

Thanks to @KalleOlaviNiemitalo, we've been able to run a series of tests
on a real VT420, so we have a good idea of how these ops are intended to
work. Our implementation does a reasonably good job of matching that
behavior, but we don't yet support paging, so we don't have the DECCRA
ability to copy between pages, and we also don't have the concept of
"unoccupied" cells, so we can't support that aspect of the streaming
operations.

It's also worth mentioning that the VT420 doesn't have colors, so we
can't be sure exactly how they are meant to interpreted. However, based
on the way the other attribute are handled, and what we know from the
DEC STD 070 documentation, I think it's fair to assume that our handling
of colors is also reasonable.

[carlos-zamora]

Looks good to me! Thanks!

[lhecker]

LGTM, but I did have an idea...

[ghost]

Hello @lhecker!

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[DHowett]

Outstanding as always. Thanks James!

[ghost]

🎉Windows Terminal Preview v1.17.1023 has been released which incorporates this pull request.:tada:

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