refactor: Migrate webviews from React 16 + react-bootstrap to React 19 + @vscode-elements/elements (#1616)

* Migrate webviews from React 16 + react-bootstrap to React 19 + @vscode-elements/elements

- Upgrade React 16.14.0 to React 19.x with react-jsx transform
- Replace deprecated @vscode/webview-ui-toolkit with @vscode-elements/elements (Lit-based)
- Replace react-bootstrap components with native HTML + custom SCSS
- Add custom Bootstrap-equivalent utility classes in vscode.scss
- Add TypeScript declarations for vscode-elements web components
- Migrate all webview entry points to React 19 createRoot API
- Convert class components to functional components
- Update webpack config for React 19 compatibility
- Fix tas-client version compatibility (override to ~0.2.33)

* fix: derive AWT action at render time without mutating shared groups array

* fix: add fallback for --design-unit CSS variable

@vscode-elements/elements does not define --design-unit (was provided
by @vscode/webview-ui-toolkit). Add fallback value of 4 so spacing
utilities (mr-*, ml-*, pt-*, etc.) resolve correctly.

* fix(test-plans): use self-contained Maven fixture for resolve-unknown-type plan (#1617)

The plan previously pointed at redhat-developer/vscode-java's salut Maven fixture, which configures maven-compiler-plugin with <source>1.7</source>/<target>1.7</target>. On the CI runners (which install only JDK 21) this puts the workspace in a state where JDT reports compliance warnings on the pom but skips full semantic analysis on the Java source -- the inserted `Gson gson;` field never produces a `Gson cannot be resolved to a type` diagnostic, so navigateToError can never find the error and applyCodeAction `Resolve unknown type` is unreachable.

Older versions of @vscjava/vscode-autotest masked this failure mode by silently pressing Enter on whatever the first Code Action happened to be; once that fallback was removed upstream the plan started reliably failing in scheduled runs (e.g. actions/runs/25419116469).

Add a minimal self-owned Maven fixture under test-fixtures/maven-resolve-type that explicitly targets JDK 11 (<release>11</release>), matching the JDK installed by the workflow. Locally this brings navigateToError from a 30s timeout to ~8s and the full plan to 6/6 passing.

Co-authored-by: copilot <copilot@local>
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
Co-authored-by: chagong <831821+chagong@users.noreply.github.com>

* ci: add autotest cases (#1619)
Co-authored-by: chagong <831821+chagong@users.noreply.github.com>

---------

Co-authored-by: wenyt <75360946+wenytang-ms@users.noreply.github.com>
Co-authored-by: copilot <copilot@local>
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
Co-authored-by: chagong <831821+chagong@users.noreply.github.com>

Author: 4 people

package-lock.json

@@ -347,9 +347,8 @@
     "@types/lodash": "^4.14.186",
     "@types/node": "20.x",
     "@types/path-exists": "^4.0.2",
-    "@types/react": "^17.0.50",
-    "@types/react-dom": "^16.9.16",
-    "@types/react-redux": "^7.1.24",
+    "@types/react": "^19.0.0",
+    "@types/react-dom": "^19.0.0",
     "@types/semver": "^7.7.1",
     "@types/vscode": "^1.74.0",
     "@types/winreg": "^1.2.31",
@@ -379,29 +378,29 @@
     "vscjava.vscode-java-dependency"
   ],
   "dependencies": {
-    "@iconify-icons/codicon": "1.2.8",
-    "@iconify/react": "^1.1.4",
-    "@reduxjs/toolkit": "^1.8.6",
+    "@reduxjs/toolkit": "^2.0.0",
+    "@vscode-elements/elements": "^2.5.0",
     "@vscode/codicons": "^0.0.44",
-    "@vscode/webview-ui-toolkit": "1.4.0",
     "@xmldom/xmldom": "^0.8.13",
     "axios": "^1.15.0",
-    "bootstrap": "^4.6.2",
+    "bootstrap": "^5.3.8",
     "compare-versions": "^6.1.1",
     "expand-home-dir": "0.0.3",
     "expand-tilde": "^2.0.2",
     "fs-extra": "^11.3.3",
     "hdr-histogram-js": "^3.0.1",
     "highlight.js": "11.11.1",
     "jdk-utils": "^0.4.4",
-    "jquery": "^3.6.1",
+    "jquery": "^4.0.0",
     "lodash": "^4.18.1",
-    "react": "^16.14.0",
-    "react-bootstrap": "^1.6.6",
-    "react-dom": "^16.14.0",
-    "react-redux": "^7.2.9",
+    "react": "^19.0.0",
+    "react-dom": "^19.0.0",
+    "react-redux": "^9.0.0",
     "semver": "^7.7.4",
     "vscode-extension-telemetry-wrapper": "^0.15.2",
     "vscode-tas-client": "^0.1.75"
+  },
+  "overrides": {
+    "tas-client": "~0.2.33"
   }
 }