[LSP Completion Performance] Incremental sychronization (aka byte-ranges) and debounce `textDocument/didChange`

Hello ALE team,

This issue was invited by @w0rp in [this Reddit post](https://www.reddit.com/r/vim/comments/10mjx5p/dense_analysis_is_now_the_nonprofit_company_that/j8x6sz4/).

Firstly, I come from a position of ignorance about what strategy ALE currently uses with respect to LSP completion latency. If ALE already uses debouncing and byte-ranges, with respect to auto-completion, then please close this issue.

My history in the LSP space was firstly with the excellent [LSC](https://github.com/natebosch/vim-lsc) plugin and then to Neovim's native LSP client.

Initially Neovim's pure Lua LSP client performed worse than LSC (coded in Vimscript). Nate Bosch (LSC author) had implemented a very efficient client when it came to auto-completion performance; he debounced `didChange` events and in addition only sent byte-ranges to the Language Server. By contrast Neovim LSP (early on) did no debouncing and sent the full text buffer for each `didChange` event.

What is debouncing `didChange` events? Basically, when in insert mode (doing edits) don't send `didChange` until a pause longer than the debounce interval has occurred. In LSC's case that is 500ms as [noted here](https://github.com/natebosch/vim-lsc/blob/master/doc/lsc.txt#L232). The Neovim LSP discussion around debouncing is [noted here](https://github.com/neovim/neovim/pull/14119).

Closely related is the topic of byte-ranges; which are small snippets indicating the delta since the last `didChange` event. LSC has always used byte-ranges; Neovim LSP did not until I created [this issue](https://github.com/neovim/neovim/issues/13049) which then resulted in [this PR](https://github.com/neovim/neovim/issues/14093). It's a complex problem, but one that LSC already solved. Initally the Neovim team just used that LSC algorithm (with appropriate attribution). ALE could do the same thing, if incremental synchronization/byte-ranges are not currently employed.

The combination of byte-ranges (incremental synchronization) with debouncing proved hugely beneficial to auto-completion performance (with certain slower Language Servers). LSC already implements solutions, in Vimscript, to these issues. LSC is permissively licensed; Neovim did leverage the LSC algorithm.

Feel free to contemplate these suggestions, or to close if not applicable.

Best regards.