fix(java): reject unusable language server JDKs (#2184)

An installed JDK that cannot run, such as an Intel-only JDK on Apple silicon, was registered as a project runtime and could crash Java language server initialization even with a working JDK selected. Each JDK's executable is now probed before selection, off the UI thread and outside the cache lock; unusable JDKs are left out, working Java 8 runtimes stay, and macOS bundle paths are accepted. An explicit choice that cannot run reports its actual executable. Since JDT keeps VM installs in its workspace, a project with an excluded JDK gets one fresh workspace; everyone else keeps their path.

Fixes #1668

src/platform/locales/text/en.json

@@ -1,4 +1,5 @@
 {
+  "The language server Java executable ({path}) cannot run on this machine. Choose a working JDK in {setting}, or set it to Auto.": "The language server Java executable ({path}) cannot run on this machine. Choose a working JDK in {setting}, or set it to Auto.",
   "Input queue is full (4 MiB or 1024 writes); input was not sent.": "Input queue is full (4 MiB or 1024 writes); input was not sent.",
   "Cannot write to terminal": "Cannot write to terminal",
   "Docker": "Docker",

src/platform/locales/text/zh.json

@@ -1,4 +1,5 @@
 {
+  "The language server Java executable ({path}) cannot run on this machine. Choose a working JDK in {setting}, or set it to Auto.": "语言服务器的 Java 可执行文件（{path}）无法在此机器上运行。请在 {setting} 中选择可正常运行的 JDK，或设为自动。",
   "Input queue is full (4 MiB or 1024 writes); input was not sent.": "输入队列已满（4 MiB 或 1024 次写入）；本次输入未发送。",
   "Cannot write to terminal": "无法写入终端",
   "Docker": "Docker",