New doc parser. Parses in <2ms; simplifies codebase.

- Doc parsing is now done only in the frontend.
- The scala parser has been eliminated. We were using it for docs and a
  few odd cases, including to run some tests. Some syntax cases that
  only occurred in compiler tests are treated differently in the new
  parser. Mainly these relate to type signatures and annotations. Some
  of these cases should be handled in translation. #5894 tracks triaging
  these cases and re-enabling the affected tests.
- The option to run the old searcher has been removed, as it is obsolete
  and was already broken before this.
- Some interfaces used only by the old searcher have been removed.

Cargo.toml

@@ -18,6 +18,7 @@ members = [
   "build/deprecated/rust-scripts",
   "build/shader-tools",
   "lib/rust/*",
+  "lib/rust/parser/doc-parser",
   "lib/rust/parser/src/syntax/tree/visitor",
   "lib/rust/parser/jni",
   "lib/rust/parser/generate-java",

app/gui/Cargo.toml

@@ -16,6 +16,7 @@ enso-data-structures = { path = "../../lib/rust/data-structures" }
 enso-debug-api = { path = "../../lib/rust/debug-api" }
 enso-debug-scene = { path = "view/examples" }
 enso-frp = { path = "../../lib/rust/frp" }
+enso-doc-parser = { path = "../../lib/rust/parser/doc-parser" }
 enso-prelude = { path = "../../lib/rust/prelude" }
 enso-profiler = { path = "../../lib/rust/profiler" }
 enso-executor = { path = "../../lib/rust/executor" }
@@ -34,7 +35,6 @@ ensogl-drop-manager = { path = "../../lib/rust/ensogl/component/drop-manager" }
 fuzzly = { path = "../../lib/rust/fuzzly" }
 ast = { path = "language/ast/impl" }
 parser = { path = "language/parser" }
-parser-scala = { path = "language/parser-scala" }
 ide-view = { path = "view" }
 engine-protocol = { path = "controller/engine-protocol" }
 json-rpc = { path = "../../lib/rust/json-rpc" }