UIA: more intelligent word boundaries

### Windows Terminal version (or Windows build number)

OpenConsole commit 5deb332

### Other Software

NVDA 2021.3

### Steps to reproduce

Move by word in a UIA console containing the following text:

Loading file c:\test.json

### Expected Behavior

In Microsoft Word, NVDA splits the word boundaries as follows:

``` python
['Loading ', 'file ', 'c', ':\\', 'test', '.', 'json']
```

### Actual Behavior

In conhost, NVDA splits the words as follows:

``` python
['Loading ', 'file ', 'c:\\test.json \r\n ']
```

Reproduce the issue in a UIA console using the text "Loading file c:\test.json" with NVDA 2021.3, then compare conhost's word boundaries with Microsoft Word's behavior. Done means word navigation separates the drive, path, extension, and surrounding words as shown in the expected output.

Written by the indexing model from the issue text.