test(lsp): smoke-test everyday code intelligence per language with real servers (#1299)

* test(lsp): smoke-test everyday code intelligence per language with real servers

A new ide-host integration test drives completion, go to definition, Find
Usages, hover, diagnostics with a quick fix, an intention, formatting and
rename on each language's fixtures/ project, through the ops the app's
commands call and the language server the app starts by default:
TypeScript (vtsls), Python (basedpyright + Ruff), Rust (rust-analyzer),
Go (gopls), Java (jdtls) and Kotlin (kotlin-lsp). A failure names the
language and the operation.

The tests are ignored by default; a Language smoke workflow installs pinned
server versions and runs one language per job on changes to crates/,
languages/ and fixtures/. Adds fixtures/java-app (Maven, JDK 21) for Java.

* test(lsp): rename TypeScript from a usage and check Rust errors while typing

Covers the fixes the smoke test turned up: a TypeScript rename started at a
call site in another file renames the declaration (#1301), and rust-analyzer's
own diagnostics and fixes arrive without saving (#1306).

fixtures/java-app/.gitignore

@@ -0,0 +1 @@
+target/