Add support for the "crossed-out" graphic rendition attribute

[j4james]

This PR adds support for the ANSI crossed-out graphic rendition
attribute, which is enabled by the SGR 9 escape sequence.

• Support for the escape sequences and storage of the attribute was
  originally added in Add support for passing through extended text attributes, like… #2917.
• Support for drawing the strikethrough effect in the grid line renderer
  was added in Refactor grid line renderers with support for more line types #7107.

Since the majority of the code required for this attribute had already
been implemented, it was just a matter of activating the
GridLines::Strikethrough style in the Renderer::s_GetGridlines
method when the CrossedOut attribute was set.

VALIDATION

There were already some unit tests in place in VtRendererTest and the
ScreenBufferTests, but I've also now extended the SGR tests in
AdapterTest to cover this attribute.

I've manually confirmed the first test case from #6205 now works as
expected in both conhost and Terminal.

Closes #6205

[j4james]

Note that I've marked this as closing #6205, although there is actually a second test case in that issue that isn't covered by this PR - using a combining long stroke Unicode character to achieve a strikethrough effect. That seems like it should be a completely separate issue, though, and wasn't something that the OP was particularly concerned about anyway.

[DHowett]

Yeah, this should close #6205. I'd prefer to track combining characters of all sorts with #1472 😄

[DHowett]

I love me a good stackable PR that builds so cleanly on prior work. 😄
Thank you

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[ghost]

🎉Windows Terminal Preview v1.3.2382.0 has been released which incorporates this pull request.:tada:

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