Move security manager codebases files to plugin-metadata (#65243)

The codebases files are hints that allow the test framework to map
codebase names required by plugin security policy files to urls that may
exist as classes directories on disk. These files end up in the same
test resources directory in gradle, but in eclipse they exist in
different directories. This commit reorganizes the files so they exist
within the same plugin-metadata source, thereby existing in the same
output directory used by tests. Finally, the codebases files are
filtered out of the final jar within the plugin build.

buildSrc/src/main/groovy/org/elasticsearch/gradle/plugin/PluginBuildPlugin.groovy

@@ -208,7 +208,11 @@ class PluginBuildPlugin implements Plugin<Project> {
         // create the actual bundle task, which zips up all the files for the plugin
         TaskProvider<Zip> bundle = project.tasks.register('bundlePlugin', Zip) {
             from buildProperties
-            from pluginMetadata // metadata (eg custom security policy)
+            from(pluginMetadata) {
+                // metadata (eg custom security policy)
+                // the codebases properties file is only for tests and not needed in production
+                exclude 'plugin-security.codebases'
+            }
             /*
              * If the plugin is using the shadow plugin then we need to bundle
              * that shadow jar.

plugins/transport-nio/src/main/plugin-metadata/plugin-security.codebases

@@ -0,0 +1,2 @@
+elasticsearch-nio: org.elasticsearch.nio.ChannelFactory
+netty-common: io.netty.util.NettyRuntime