[Searchbar + RTL] Moving cursor with arrow keys is a bit broken with RTL

### Expected
Moving the cursor in the search bar with arrow keys for RTL should be consistent, and comply with the scheme used for example in 'Notes' app.

### Observed
Inability to move cursor to the right immediately. It doesn't matter if the app was launched in usual mode or with
NSForceRightToLeftWritingDirection enabled.

### Reproduced
1. Have RTL selected (e.g. use Hebrew)
2. Enter the RTL text into searchbar ~> the cursor will be placed at the left of text
3. Press right arrow key ~> cursor does not move (bug)
4. Pressing left key once, and then using right key allows to navigate.

The video shows some context, but can't show at which time keyboard keys were pressed.

https://user-images.githubusercontent.com/73365754/105819283-a619cb80-5fc0-11eb-926c-903ecc953969.mov

Make|Model|macOS Version|App Version
-|-|-|-
Mac|MBP 16|11.1|2.6

Start by reproducing the issue from the search bar with Hebrew or another RTL language, following the listed arrow-key steps. Done means the cursor moves consistently with the expected RTL behavior, including moving right immediately after entering text.

Written by the indexing model from the issue text.