## Summary of the Pull Request
1) Improves the performance of word-recognition operations such as word
navigation in UIA and selection.
2) Fixes a bug where attempting to find the next word in UIA, when none
exists, would hang
3) TraceLogging code only runs when somebody is listening
## Detailed Description of the Pull Request / Additional comments
- The concept of a delimiter class got moved to the CharRow.
- The buffer iterator used to save a lot more information than we needed
- I missed updating a tracing function after making GetSelection return
one text range. That is fixed now.
## Validation Steps Performed
Performed Word Navigation under Narrator and NVDA.
NOTE: The release build should be used when testing to optimize
performance
Closes#4703
