Remove usages of old safe math

[miniksa]

There are approximately 79 uses of old safe math. (a.k.a. the LongAdd, ShortAdd, and friends from intsafe.h).

This task represents removing them and transitioning them to an appropriate safe/saturating math function from the chromium safe math library introduced in #4144.

After removing usages of the old safe math functions, also remove the intsafe.h header.

Files with old safe math as of this writing:

• TerminalControl: TSFInputControl.cpp
• TerminalCore: TerminalDispatch.cpp
• TerminalCore: TerminalSelection.cpp
• Host: directio.cpp
• RendererGdi: invalidate.cpp
• RendererGdi: math.cpp
• RendererGdi: paint.cpp
• RendererVt: paint.cpp
• TerminalAdapter: adaptDispatch.cpp
• Types: viewport.cpp
• Types: WindowUiaProviderBase.cpp

[miniksa]

If @j4james doesn't take this, whomever takes this should consult with @j4james on the ones in adaptDispatch.cpp because they should likely be saturating math instead of failing when exceeding bounds as they are today.

[j4james]

I don't mind doing this eventually, but I have bunch of stuff in progress that I would like to try and get finished first. If anyone else wants to take it on, though, I would recommend waiting at least until #3628 is merged, because there is a fair amount of safe math code in AdaptDispatch that will be nuked by that PR, so you'll be wasting your time if you're trying to refactor that.

On a similar note, I expect issue #3849 will end up replacing most, if not all, of the TerminalDispatch code. That said, it may be a long time before that happens, so it's possibly still worth cleaning up the existing code in the mean time.

[j4james]

One other thing I wanted to add: there is another category of intsafe routines which I think isn't covered by the 79 uses mentioned above, and that is the type conversion functions, e.g. SizeTToShort. In the VT code, I think many of those would probably need to be converted to something like a saturated_cast when using the new chromium lib.