vim netrw (#7962)

- Tidy up vim netrw bindings (c.f.
https://github.com/zed-industries/zed/issues/4270,
https://github.com/zed-industries/zed/pull/7757)
- Add vim commands for panels

Release Notes:

- vim: add commands to toggle panels `:E[xplore]`, `:C[ollab]`,
`:Ch[at]`, `:N[otification]`, `:A[I]`, `:te[rm]` (or `:T[erm]`).