ECJ upgrade

Replacement of ant eclipse-warnings by a new task using the CheckerFramework is happening as part of CASSANDRA-18239 . Thus, I upgraded ecj to the latest possible version that supports both JDK11 and 17 for the Java UDFs and removed ant eclipse-warnings (including eclipse_compiler.properties). I do not entirely remove the ant target from build.xml. I left a fake empty task to confuse Jenkins as there are ongoing changes for trunk and cassandra-builds, so I decided to make changes there when the concurrent changes related to moving in-tree the build scripts for trunk are done. Though I removed the task from CircleCI as that was quick and easy. I will open a follow-up task for Jenkins.  I did not find a changelog so I looked into the ECJ changes here - https://github.com/eclipse-jdt/eclipse.jdt.core/compare/R4_6_maintenance...R4_27_maintenance We will be able to commit the patch to trunk when we drop JDK8 as the new version is JDK11+. All tests pass. I did minor changes: added the new methods of ICompilationUnit to our implementation - ECJCompilationUnit. At this point I think keeping the unnamed module Is fine for us. Bumped the version of CompilerOptions to 11 The compiler has added enablePreviewFeatures, enableJdtDebugCompileMode, ignoreUnnamedModuleForSplit which are false by default. I keep this as I do not believe we want to enable those. I also kept the ReportDeprecations untouched - it is enabled by default. CI looks good and fixes the two tests that were reported broken with JDK17 as our ECJ version was not supporting JDK17. (org.apache.cassandra.cql3.validation.entities.UFJavaTest, org.apache.cassandra.cql3.validation.entities.UFSecurityTest) CircleCI run #2380 CI:  https://app.circleci.com/pipelines/github/ekaterinadimitrova2/cassandra?branch=18190-udf PR: https://github.com/apache/cassandra/pull/2429   I also tested locally the fake task that it completes successfully without running anything.