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/README.md

@@ -34,7 +34,7 @@ plugins/
    ├─ regex-tester/           # html view talking to its code, settings, the editor's selection
    └─ license-header/         # file-opened events, quick fix, project scan in a task
 sdk/rust/openidea-plugin/     # the Rust SDK (host API, Plugin trait, mock host)
-crates/ide-plugin/tests/fixtures/  # test plugins: hello, jobs, language-toy, misbehave, semantic-tokens
+crates/ide-plugin/tests/fixtures/  # test plugins: hello, jobs, language-toy, misbehave, semantic-tokens, hover
 ```
 
 The plugin API is defined in [`wit/`](../wit/) (`openidea:[email protected]`, world
@@ -402,7 +402,7 @@ declaration matches the file's language are called (and loaded):
 
 ```toml
 [[contributes.providers]]
-kinds = ["definition", "line-markers", "completion"]  # also "inline-completion", "code-actions", "semantic-tokens"
+kinds = ["definition", "line-markers", "completion"]  # also "inline-completion", "code-actions", "semantic-tokens", "hover"
 languages = ["java", "xml"]                           # editor language ids; "*" for any
 ```
 
@@ -457,6 +457,26 @@ the language server's semantic tokens and win where they overlap one, so the
 editor's colour scheme styles them like the server's. They are asked again
 after each edit, under the edit-path budget; at most 65,536 per document.
 
+#### Hover
+
+The `hover` kind (API 1.3) adds Markdown to the hover of documents of the
+declared languages, here too including languages the plugin doesn't
+contribute. Register with `register_plugin!(MyPlugin, hover)` and implement
+`openidea_plugin::hover::HoverProvider`:
+
+```rust
+impl HoverProvider for MyPlugin {
+    fn hover(&mut self, doc: &Document, at: Position) -> Option<Hover> {
+        Some(Hover::new("**orders.index** · `GET /orders`"))
+    }
+}
+```
+
+The host asks the language server and the plugins together, under the
+edit-path budget, and shows the server's hover first, then each plugin's
+below a rule. `range`, when given, is the text the hover describes (used when
+the server names none). At most 64 KiB of Markdown per plugin.
+
 ### Network and secrets
 
 `host::fetch` makes an HTTPS request (plain HTTP only to `localhost`) to a host

plugins/official/ai-completion/dist/plugin.wasm.sources

@@ -1 +1 @@
-eb76da4bc9db84dcbad34143bac18c9ecf974276f793009791a15aab2eee291d
+9384d8964c7c05d3df06521e0d724a932fdd17608cbcede13ec2acadfab3783c

plugins/official/checkstyle/dist/plugin.wasm.sources

@@ -1 +1 @@
-0a19948927a23de81b2a453b9992e021744093cbe41ea92daa9feb2b1bc9a2a9
+9d7e857ef367eaa9748d1a2b05b7b45226c254aa578c29e1ed987c7353738acf

plugins/official/csv-editor/dist/plugin.wasm.sources

@@ -1 +1 @@
-564bfd00694f27f35f09eb0b81d341207a755528b5fe7c46c96717b3868d0f65
+3e11039d36306f51c728bf9d08030fe620de461fa5b0037700aea95c4d27714c

plugins/official/git-toolbox/dist/plugin.wasm.sources

@@ -1 +1 @@
-f3f447366fa38f9bf4911f35b6e899405b0e072ceee3ad5ea2fe90639d70fa53
+ef50957a407c9aff9999fdd197a5e72c90b7ba77aedbd7569408262ab7e158be

plugins/official/graphviz/dist/plugin.wasm.sources

@@ -1 +1 @@
-85cad466adb94f2b58e62263617e885d1c47cf70db5e8b38942bd415f0d779af
+7160b309f39fe973e67bb20d361384955aed6afe98f00db329c3026ffe923759

plugins/official/key-promoter/dist/plugin.wasm.sources

@@ -1 +1 @@
-659446eda0b50aa0fb08f6af68f7d355fcaf3342847e2e579999dcf52a7a7399
+1f1afa285a64a7f7758f08a80306d6397c8aee4d2ac7ed43369e77aae61add04

plugins/official/license-header/dist/plugin.wasm.sources

@@ -1 +1 @@
-51ef9d43315ca9d7239999c222fbf7a2c01bc85c2b40f53f34a1a8e5d31baa6d
+ddd9205da9fc947215ab90c505d8b443d0937b1dd11734e9ce94d277517c77a6

plugins/official/mybatis/dist/plugin.wasm.sources

@@ -1 +1 @@
-bdf9455c6e7c8c340c54d783f351220b38cffed36907e1b5a1f2e11801e6f5bb
+c61a0ec6ffcbd71e590e5a16a6f08f2d2772481497edc77e11914cfb3d0bfcd1

plugins/official/regex-tester/dist/plugin.wasm.sources

@@ -1 +1 @@
-7e4d00e1ea63b2eca48b9297667e04c05a9f9832f1dee2262272801d516b9a16
+e11cd0b664ae058274808bc2b2152bac2738207979758d13bc0c0cd96c38ef4f

plugins/official/solidity/dist/plugin.wasm.sources

@@ -1 +1 @@
-00cbd2dd7f0937554633ba5e533f19be85f70579c7c6fedb6fe0228f8f63bf4c
+59319cf4be14448b0126b07d074cc08c351cfd12a3de26f111c2445fe8bff664

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

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