This PR updates the `ExtensionLspAdapter` to go through the `Extension`
trait for interacting with extensions rather than going through the
`WasmHost` directly.
Release Notes:
- N/A
This PR extracts the `ExtensionIndexedDocsProvider` implementation to
the `indexed_docs` crate.
To achieve this, we introduce a new `Extension` trait that provides an
abstracted interface for calling an extension. This trait resides in the
`extension` crate, which has minimal dependencies and can be depended on
by other crates, like `indexed_docs`.
We're then able to implement the `ExtensionIndexedDocsProvider` without
having any knowledge of the Wasm-specific internals of the extension
system.
Release Notes:
- N/A
