This builds on https://github.com/neovim/neovim/pull/14112 and closes
https://github.com/neovim/neovim/issues/12326

This is mostly motivated by https://github.com/neovim/neovim/issues/12326

Client side commands might need to access the original request
parameters.

Currently this is already possible by using closures with
`vim.lsp.buf_request`, but the global handlers so far couldn't access
the request parameters.

- Fix the cursor position after applying TextEdits
- Support reversed range of TextEdit
- Invoke nvim_buf_set_text one by one

This generalizes diagnostic handling outside of just the scope of LSP.
LSP clients are now a specific case of a diagnostic producer, but the
diagnostic subsystem is decoupled from the LSP subsystem (or will be,
eventually).

More discussion at [1].

[1]: https://github.com/neovim/neovim/pull/15585

Fixes #15522

feat(lsp)!: change handler signature

Previously, the handler signature was:

  function(err, method, params, client_id, bufnr, config)

In order to better support external plugins that wish to extend the
protocol, there is other information which would be advantageous to
forward to the client, such as the original params of the request that
generated the callback.

In order to do this, we would need to break symmetry of the handlers, to
add an additional "params" as the 7th argument.

Instead, this PR changes the signature of the handlers to:

  function(err, result, ctx, config)

where ctx (the context) includes params, client_id, and bufnr. This also leaves
flexibility for future use-cases.

BREAKING_CHANGE: changes the signature of the built-in client handlers, requiring
updating handler calls