Add :tabonly and :only vim commands (#8337)

Release Notes:

- Added
[`:tabo[nly][!]`](https://neovim.io/doc/user/tabpage.html#%3Atabonly),
closes all the tabs except the active one but in the current pane only,
every other split pane remains unaffected.
The version with the `!` force closes the tabs while the one without
asks you to save or discard the changes.
- Added [`:on[ly][!]`](https://neovim.io/doc/user/windows.html#%3Aonly),
closes all the tabs *and* panes except the active one.
The version with the `!` force closes the tabs while the one without
asks you to save or discard the changes.
Since Zed does not have different splits per tab like in Neovim `:only`
works the same as it does in VscodeVim.

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Co-authored-by: Conrad Irwin <conrad.irwin@gmail.com>