Modernize Antora Build

- Use package.json so dependabot can automatically update JS dependencies
- Use @springio/antora-extensions (automatically apply default extensions
  in proper order)
- Leverage set-algolia-env-extension to manage algolia env variables
- Update to latest ui

Closes gh-32863

package.json

@@ -0,0 +1,10 @@
+{
+  "dependencies": {
+    "antora": "3.2.0-alpha.4",
+    "@antora/atlas-extension": "1.0.0-alpha.2",
+    "@antora/collector-extension": "1.0.0-alpha.3",
+    "@asciidoctor/tabs": "1.0.0-beta.6",
+    "@springio/antora-extensions": "1.11.1",
+    "@springio/asciidoctor-extensions": "1.0.0-alpha.10"
+  }
+}