Upgrade to Groovy 3.0.3 (with FindBugs workaround for groovy-templates)

Closes gh-24215

build.gradle

@@ -43,6 +43,7 @@ configure(allprojects) { project ->
 				entry 'log4j-jul'
 			}
 			dependency "org.slf4j:slf4j-api:1.7.30"
+			dependency "com.google.code.findbugs:findbugs:3.0.1"
 			dependency "com.google.code.findbugs:jsr305:3.0.2"
 
 			dependencySet(group: 'org.aspectj', version: '1.9.5') {
@@ -50,10 +51,10 @@ configure(allprojects) { project ->
 				entry 'aspectjtools'
 				entry 'aspectjweaver'
 			}
-			dependencySet(group: 'org.codehaus.groovy', version: '2.5.11') {
+			dependencySet(group: 'org.codehaus.groovy', version: '3.0.3') {
 				entry 'groovy'
 				entry 'groovy-jsr223'
-				entry 'groovy-templates'
+				entry 'groovy-templates'  // requires findbugs for warning-free compilation
 				entry 'groovy-test'
 				entry 'groovy-xml'
 			}

spring-webmvc/spring-webmvc.gradle

@@ -10,6 +10,7 @@ dependencies {
 	compile(project(":spring-expression"))
 	compile(project(":spring-web"))
 	compileOnly("javax.servlet:javax.servlet-api")
+	compileOnly("com.google.code.findbugs:findbugs")  // for groovy-templates
 	optional(project(":spring-context-support"))  // for FreeMarker support
 	optional(project(":spring-oxm"))
 	optional("javax.servlet.jsp:javax.servlet.jsp-api")