* send vim.NIL instead of not sending workspaceFolders
* read fallback rootPath and rootUri from workspaceFolders
* update documentation

closes https://github.com/neovim/neovim/issues/16352

* improve handling of multi-byte deletions

If a LSP server sent a workspace edit containing a rename the buffers
file name changed without the server receiving a close notification for
the old buffer and without the client properly re-attaching on the new
file.

This affected `Move` code-actions in nvim-jdtls, but also
`vim.lsp.buf.rename` on a class level.

* use codeunits/points instead of byte ranges when applicable
* take into account different file formats when computing range and
  sending text (dos, unix, and mac supported)
* add tests of incremental sync

* vim.ui.input is an overridable function that prompts for user input
* take an opts table and the `on_confirm` callback, see `:help vim.ui.input` for more details
* defaults to a wrapper around vim.fn.input(opts)
* switches the built-in client's rename handler to use vim.ui.input by default

Rather than treating virtual_text, signs, and underline specially,
introduce the concept of generic "handlers", of which those three are
simply the defaults bundled with Nvim. Handlers are called in
`vim.diagnostic.show()` and `vim.diagnostic.hide()` and are used to
handle how diagnostics are displayed.