Add Vim character find and till motions (#40785)

## What changed

- Add line-local `f`, `F`, `t`, and `T` motions to Vim normal mode.
- Support the motions with `c`, `d`, and `y`, including dot-repeat for changes.
- Expose separate configurable normal-mode and operator-motion bindings, while preserving existing custom keymaps that use the new defaults.
- Keep character targeting aligned to extended grapheme boundaries and skip embedded composer elements.

## Testing

- Cover forward and backward motion and operator ranges, missing and adjacent targets, cancellation, dot-repeat, custom bindings, shifted terminal key events, grapheme clusters, and embedded elements.

GitOrigin-RevId: 2610cf9a13538d9ae9b890c01417ca25316c1d60