Word UIA: Support native table extended navigation commands (#17867)
Summary of the issue:
In word, native extended table navigation commands `alt+home`,
`alt+end`, `alt+pageUp` and `alt+pageDown` are report their result (i.e.
the content of the landing cell) when using legacy document access, but
not when using UIA.
Description of user facing changes
In Word with UIA, when using the native extended table navigation
commands `alt+home`, `alt+end`, `alt+pageUp` and `alt+pageDown`, the
landing cell will now be reported.
Description of development approach
* Factorize the script for this commands to use it for legacy as well as
for UIA.
* Create separate `_inTable` methods for UIA and for legacy.
* For UIA text info's `expand` method, implement the support for cell
unit.
Testing strategy:
Manual testing for both UIA and legacy.
Known issues with pull request:
None