Add :tabonly and :only vim commands

[riccardofano]

Release Notes:

• Added :tabo[nly][!], 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][!], 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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[riccardofano]

@cla-bot check

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[ConradIrwin]

Thank you so much for adding these!