Fail Gradle build whenever a javadoc task fails

To ensure that failures in javadoc tasks do not result in documentation
silently not being generated/published, this commit sets
`failOnError = true` for all javadoc tasks.

See gh-27497
See gh-34774
Closes gh-34837

framework-api/framework-api.gradle

@@ -21,6 +21,7 @@ dependencies {
 
 javadoc {
 	title = "${rootProject.description} ${version} API"
+	failOnError = true
 	options {
 		encoding = "UTF-8"
 		memberLevel = JavadocMemberLevel.PROTECTED

gradle/spring-module.gradle

@@ -69,7 +69,7 @@ normalization {
 
 javadoc {
 	description = "Generates project-level javadoc for use in -javadoc jar"
-
+	failOnError = true
 	options {
 		encoding = "UTF-8"
 		memberLevel = JavadocMemberLevel.PROTECTED