feat(plugins): let plugins add to the hover of any language (#1931)

Plugin API 1.3 gains an optional hover-provider export (worlds plugin-hover
and hover): hover(doc, at) returns Markdown and the range it describes. A
plugin declares the hover kind under [[contributes.providers]] for any
language; the host asks it with the language server, under the edit-path
budget, and shows the server's hover first and each plugin's below a rule.
Declaring the kind needs engines.openidea ^1.3. The Rust SDK gains
openidea_plugin::hover and register_plugin!(T, hover); every shipped
component is rebuilt for the WIT change.

plugins/official/string-tools/dist/plugin.wasm.sources

@@ -1 +1 @@
-eecf2cf561dd5e3e3edbf9f67ccb479573dd538a75d4426a1d086edf0a310043
+59844ae52aa765af404b43f7895db94d0063a3a6fce5bd54bf9af680ccac357b