reconfigure branch for local builds and as scheduler for docs workflows

- set up placeholder and trigger for Deploy Docs workflow in docs-build branch
- set up placeholder and trigger for Rebuild Search Index workflow in docs-build branch
- remove obsolete Deploy Reference workflow
- upgrade Antora to 3.1
- reconfigure docs build for local build only
- add patch to support using linked worktree as Antora content source
- remove Antora extensions only needed for the production docs build

docs/spring-security-docs.gradle

@@ -6,16 +6,22 @@ plugins {
 apply plugin: 'io.spring.convention.docs'
 apply plugin: 'java'
 
+node {
+	version = "16.17.0"
+}
+
 antora {
-	antoraVersion = "3.0.0"
-	arguments = ["--fetch", "--stacktrace"]
+	antoraVersion = "3.1.0"
+	playbookFile = file("local-antora-playbook.yml")
+	arguments = ["--clean", "--stacktrace"]
 }
 
 tasks.antora {
+	dependsOn "generateAntora"
 	environment = [
-			"ALGOLIA_API_KEY" : "82c7ead946afbac3cf98c32446154691",
-			"ALGOLIA_APP_ID" : "244V8V9FGG",
-			"ALGOLIA_INDEX_NAME" : "security-docs"
+		"ALGOLIA_API_KEY" : "82c7ead946afbac3cf98c32446154691",
+		"ALGOLIA_APP_ID" : "244V8V9FGG",
+		"ALGOLIA_INDEX_NAME" : "security-docs"
 	]
 }
 
@@ -64,8 +70,6 @@ ${ymlVersions}
 	}
 }
 
-
-
 dependencies {
 	testImplementation platform(project(":spring-security-dependencies"))
 	testImplementation "com.unboundid:unboundid-ldapsdk"