## Summary of the Pull Request
Adds support for the `focusPane` action, and the `focus-pane` subcommand. These allow the user to focus a pane by it's ID.
* `focusPane` accepts an `id`, identifying the id of the pane to focus.
* `focus-pane`, `fp` requires the parameter `--target,-t` to ID the pane it's going to focus.
## PR Checklist
* [x] Closes#5803
* [x] Closes#5464
* [x] I work here
* [x] Tests added/passed
* [ ] Requires documentation to be updated - oh no
## Detailed Description of the Pull Request / Additional comments
The ID isn't _totally_ useful right now, since users can't see them. But they're there, and used in-order. This is just slightly more ergonomic for complicated commandlines than `mf up; mf left`
## Validation Steps Performed
Tested in command palette
Tested a variety of commandlines. `wtd -w 0 mf down ; sp` and `wtd -w 0 fp -t 1 ; sp` gave me special difficulty.
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