## Summary of the Pull Request
Updates our `UiaTextRange` to no longer treat the end of the buffer as the "document end". Instead, we consider the "document end" to be the line beneath the cursor or last legible character (whichever is further down). In the event where the last legible character is on the last line of the buffer, we use the "end exclusive" position (left-most point on a line one past the end of the buffer).
When movement of any kind occurs, we clamp each endpoint to the document end. Since the document end is an actual spot in the buffer (most of the time), this should improve stability because we shouldn't be pointing out-of-bounds anymore.
The biggest benefit is that this significantly improves the performance of word navigation because screen readers no longer have to take into account the whitespace following the end of the prompt.
Word navigation tests were added to the `TestTableWriter` (see #10886). 24 of the 85 tests were failing, however, they don't seem to interact with the document end, so I've marked them as skip and will fix them in a follow-up. This PR is large enough as-is, so I'm hoping I can take time in the follow-up to clean some things on the side (aka `preventBoundary` and `allowBottomExclusive` being used interchangeably).
## References
#7000 - Epic
Closes#6986Closes#10925
## Validation Steps Performed
- [X] Tests pass
- [X] @codeofdusk has been personally testing this build (and others)
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