## Summary of the Pull Request
Adds a execute commandline action (`wt`), which lets a user bind a key to a specific `wt` commandline. This commandline will get parsed and run _in the current window_.
## References
* Related to #4472
* Related to #5400 - I need this for the commandline mode of the Command Palette
* Related to #5970
## PR Checklist
* [x] Closes oh, there's not actually an issue for this.
* [x] I work here
* [x] Tests added/passed
* [ ] Requires documentation to be updated - yes it does
## Detailed Description of the Pull Request / Additional comments
One important part of this change concerns how panes are initialized at runtime. We've had some persistent trouble with initializing multiple panes, because they rely on knowing how big they'll actually be, to be able to determine if they can split again.
We previously worked around this by ignoring the size check when we were in "startup", processing an initial commandline. This PR however requires us to be able to know the initial size of a pane at runtime, but before the parents have necessarily been added to the tree, or had their renderer's set up.
This led to the development of `Pane::PreCalculateCanSplit`, which is very highly similar to `Pane::PreCalculateAutoSplit`. This method attempts to figure out how big a pane _will_ take, before the parent has necessarily laid out.
This also involves a small change to `TermControl`, because if its renderer hasn't been set up yet, it'll always think the font is `{0, fontHeight}`, which will let the Terminal keep splitting in the x direction. This change also makes the TermControl set up a renderer to get the real font size when it hasn't yet been initialized.
## Validation Steps Performed
This was what the json blob I was using for testing evolved into
```json
{
"command": {
"action":"wt",
"commandline": "new-tab cmd.exe /k #work 15 ; split-pane cmd.exe /k #work 15 ; split-pane cmd.exe /k media-commandline ; new-tab powershell dev\\symbols.ps1 ; new-tab -p \"Ubuntu\" ; new-tab -p \"haunter.gif\" ; focus-tab -t 0",
},
"keys": ["ctrl+shift+n"]
}
```
I also added some tests.
# TODO
* [x] Creating a `{ "command": "wt" }` action without a commandline will spawn a new `wt.exe` process?
- Probably should just do nothing for the empty string
d0ff5f6b5e