Update Helix's handling of the following actions in order to ensure that
selections are created when using subword motions:

* `vim::NextSubwordStart`
* `vim::NextSubwordEnd`
* `vim::PreviousSubwordStart`
* `vim::PreviousSubwordEnd`

The handling of these motions was done by
`vim::helix::Vim::helix_move_and_collapse`, which simply moved the
cursor without doing any selection. This commit updates it to correctly
use both `vim::helix::Vim::helix_find_range_forward` and
`vim::helix::Vim::helix_find_range_backward`.

The added tests have been confirmed against Helix's behavior of the following commands:

* `move_next_sub_word_start`
* `move_prev_sub_word_start`
* `move_next_sub_word_end`
* `move_prev_sub_word_end`

Closes #41767

Release Notes:

- Fix subword motions in Helix mode to select traversed text

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Co-authored-by: Conrad Irwin <conrad.irwin@gmail.com>
Co-authored-by: dino <dinojoaocosta@gmail.com>