component: Replace linkme with inventory (#30705)

This PR replaces the use of `linkme` with `inventory` for the component
preview registration.

Release Notes:

- N/A

crates/diagnostics/Cargo.toml

@@ -23,7 +23,6 @@ futures.workspace = true
 gpui.workspace = true
 indoc.workspace = true
 language.workspace = true
-linkme.workspace = true
 log.workspace = true
 lsp.workspace = true
 markdown.workspace = true