Instead cause some changes to screen state and use screen:expect().

Problem:
`vim.lsp.util.rename()` deletes the buffers that are affected by
renaming. This has undesireable side effects. For example, when renaming
a directory, all buffers under that directory are deleted and windows
displaying those buffers are closed. Also, buffer options may change
after renaming.

Solution:
Rename the buffers with :saveas.

An alternative approach is to record all the relevant states and restore
it after renaming, but that seems to be more complex. In fact, the older
version was attempting to restore the states but only partially and
incorrectly.

Problem:
  vim._watch.watchdirs has terrible performance.

Solution:
  - On linux use fswatch as a watcher backend if available.

  - Add File watcher section to health:vim.lsp. Warn if watchfunc is
    libuv-poll.

- Rename watch.poll to watch.watchdirs
- Unify how include and exclude is applied
- Improve type hints

Problem:
After `rename()`, the undo information for the renamed file(s) are lost.

Solution:
Rename the undofile as well.

Previously rename would unconditionally read the to-be-renamed file from the
disk and write it to the disk. This is redundant in some cases

If the file is not already loaded, it's not attached to lsp client, so nvim
doesn't need to care about this file.
If the file is loaded but has no change, it doesn't need to be written.

Co-authored-by: wookayin <wookayin@gmail.com>
Co-authored-by: clason <c.clason@uni-graz.at>
Co-authored-by: Lewis Russell <me@lewisr.dev>