…ent (zed-industries#50697)

Closes zed-industries#47917

Currently, during remote development, Zed uses the first available local
LSP adapter to handle all label computing. This isn't ideal and causes
bugs because different adapters may expect different label formats. By
leveraging the `all_capable_for_proto_request` method, we can now
retrieve the specific language server name and use it as a key to find
the correct LSP adapter for label population. Even if this lookup fails,
we can still fall back to the first adapter, so this PR should provide
more accurate label population than before.

This addresses the root cause of zed-industries#47917, which stems from two main
issues. For example, in remote Python development, the `basedpyright`
adapter might incorrectly handle labels even when the remote server is
actually `ty`. The completion items returned by `ty` are slightly
different from `basedpyright`: `ty` stores labels in
`labelDetails.detail`, while basedpyright uses
`labelDetails.description`. By matching the correct adapter, we ensure
labels are populated properly for completion items.
```json
// RPC message returned by `ty`, label is in `labelDetails.detail`
{
  ...
  "labelDetails": { "detail": " (import pathlib)" },
  ...
}

// RPC message returned by `basedpyright`, label is in `labelDetails.description`
{
  ...
  "labelDetails": { "description": "pathlib" },
  ...
}
```
Additionally, adapters registered via `register_available_lsp_adapter`
are lazy-loaded into the `LanguageRegistry` (which is the case for `ty`
before). In remote scenarios, the adapter might be loaded on the remote
server but not on the local host, making it hard to find in
`lsp_adapters`. This is partially resolved in zed-industries#50662, and combined with
this PR, we can fully address zed-industries#47917.

There is still more to do, however. In some cases, we still can't find
the correct local LSP adapter if the local host lacks the registry that
the remote server has; this typically happens when the adapter is
registered via `register_available_lsp_adapter`. I've opened a feature
discussion zed-industries#49178 to track this. If it's decided that this needs further
refinement, I'm happy to continue working on it.


Before you mark this PR as ready for review, make sure that you have:
- [ ] Added a solid test coverage and/or screenshots from doing manual
testing
- [x] Done a self-review taking into account security and performance
aspects
- [x] Aligned any UI changes with the [UI
checklist](https://github.com/zed-industries/zed/blob/main/CONTRIBUTING.md#uiux-checklist)

Release Notes:

- Fixed missing labels for `ty` completion items in remote development.