Some cell types do not focus the input after entering edit mode

[seancolsen]

Originally reported by @pavish.

Steps to reproduce

1. Double click a Number cell to enter edit mode.
2. Press Left and Right arrow keys.
3. Expect the key presses to move the caret within the number input.
4. Instead observe that the arrow keys horizontally scroll the sheet. This is because the number input within the cell is not automatically focused after the cell enters edit mode.

This is a regression introduced in #2957.