fix(editor): say when a file is outside the language server's projects (#1046)

jdtls only checks the syntax of a Java file outside every module's source
folders (or outside any imported project) and answers navigation with
nothing. The editor then said only "Cannot find declaration to go to", and
the server's explanation was a warning squiggle on line 1.

- A banner above the editor explains it while the server reports it, for
  jdtls (not on the classpath of a project / non-project file), gopls (no
  package, build constraints — this replaces the Go-only banner) and
  rust-analyzer (unlinked file). For Java it offers the Maven / Gradle reload
  when available.
- Go to Declaration / Implementation / Type Declaration that finds nothing
  in such a file gives the reason in its hint.

Fixes #827

src/platform/locales/text/zh.json

@@ -5581,5 +5581,11 @@
   "External file changes sync may be slow": "外部文件更改同步可能较慢",
   "recursive": "递归",
   "Java project import failed": "Java 项目导入失败",
-  "The Java project cannot be imported because these files use a name Windows reserves for devices: {paths}. Delete or rename them, then restart the Java language server.": "无法导入 Java 项目，因为这些文件使用了 Windows 保留的设备名：{paths}。请删除或重命名这些文件，然后重启 Java 语言服务器。"
+  "The Java project cannot be imported because these files use a name Windows reserves for devices: {paths}. Delete or rename them, then restart the Java language server.": "无法导入 Java 项目，因为这些文件使用了 Windows 保留的设备名：{paths}。请删除或重命名这些文件，然后重启 Java 语言服务器。",
+  "This file is outside the source folders of its Java module: only syntax errors are reported, and navigation and completion don't work.": "此文件不在所属 Java 模块的源码目录中：只报告语法错误，跳转和补全不可用。",
+  "This file does not belong to an imported Java project: only syntax errors are reported, and navigation and completion don't work.": "此文件不属于已导入的 Java 项目：只报告语法错误，跳转和补全不可用。",
+  "This Go file belongs to no package of the workspace: code insight is limited.": "此 Go 文件不属于工作区中的任何包：代码洞察功能受限。",
+  "This Rust file is not included in any crate: rust-analyzer can't offer code insight for it.": "此 Rust 文件未包含在任何 crate 中：rust-analyzer 无法为它提供代码洞察。",
+  "Reload Maven Projects": "重新加载 Maven 项目",
+  "Reload Gradle Project": "重新加载 Gradle 项目"
 }