refactor(lsp): stateful data abstraction, vim.lsp.Capability #34639

Problem:
Closes #31453

Solution:
Introduce `vim.lsp.Capability`, which may serve as the base class for
all LSP features that require caching data. it
- was created if there is at least one client that supports the specific method;
- was destroyed if all clients that support the method were detached.

- Apply the refactor for `folding_range.lua` and `semantic_tokens.lua`.
- Show active features in :checkhealth.

Future:
I found that these features that are expected to be refactored by
`vim.lsp.Capability` have one characteristic in common: they all send
LSP requests once the document is modified. The following code is
different, but they are all for this purpose.

- semantic tokens:
https://github.com/neovim/neovim/blob/fb8dba413f2bcaa61c15d1854b28112e3e91a035/runtime/lua/vim/lsp/semantic_tokens.lua#L192-L198
- inlay hints, folding ranges, document color
https://github.com/neovim/neovim/blob/fb8dba413f2bcaa61c15d1854b28112e3e91a035/runtime/lua/vim/lsp/inlay_hint.lua#L250-L266

I think I can sum up this characteristic as the need to keep certain
data synchronized with the latest version computed by the server.
I believe we can handle this at the `vim.lsp.Capability` level, and
I think it will be very useful.

Therefore, my next step is to implement LSP request sending and data
synchronization on `vim.lsp.Capability`, rather than limiting it to the
current create/destroy data approach.

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