Fix ESQL tests in IntelliJ (elastic#107313)

Landing elastic#107018 broke running ESQL unit tests in IntelliJ. It has
*something* to do with turning on the stringtemplate plugin in the esql
project but I don't really know what. After that PR we'd often get
errors about trying to regenerate evaluators twice. I dunno. This fixes
it. But I don't really know why.

The way this fixes it is by making the `esql` project more like the
`copmute` project. It makes sense that that would help - they both have
the same code generation configuration. Anyway, the operative change is
landing the generated files in the same place as the `compute` project.
Thus all of the file moves.

Again, I have no idea why this works. It's build black magic and I just
shook it until it worked. Most of the credit goes to git-bisect for
finding the commit that broke this.

.gitignore

@@ -68,4 +68,4 @@ testfixtures_shared/
 
 # Generated
 checkstyle_ide.xml
-x-pack/plugin/esql/gen/
+x-pack/plugin/esql/src/main/generated-src/generated/

x-pack/plugin/esql/build.gradle

@@ -40,23 +40,10 @@ dependencies {
   internalClusterTestImplementation project(":modules:mapper-extras")
 }
 
-/*
- * IntelliJ will always put the java files generated by the annotation processor
- * into src/main/java/generated so we make gradle play along. This block makes
- * it put the generated files into the same spot and the next block stops it from
- * trying to compile the generated files in the regular compile - it'll regenerate
- * them and *then* compile them.
- */
 tasks.named("compileJava").configure {
-  options.compilerArgs.addAll(["-s", "${projectDir}/src/main/java/generated"])
-}
-
-tasks.named("javadoc").configure {
-  include("${projectDir}/src/main/java/generated")
-}
-
-sourceSets.main.java {
-  exclude 'generated/**'
+  options.compilerArgs.addAll(["-s", "${projectDir}/src/main/generated"])
+  // IntelliJ sticks generated files here and we can't stop it....
+  exclude { it.file.toString().startsWith("${projectDir}/src/main/generated-src/generated") }
 }
 
 tasks.named("test").configure {
@@ -149,7 +136,8 @@ pluginManager.withPlugin('com.diffplug.spotless') {
       // for some reason "${outputPath}/EsqlBaseParser*.java" does not match the same files...
       targetExclude "src/main/java/org/elasticsearch/xpack/esql/parser/EsqlBaseLexer*.java",
         "src/main/java/org/elasticsearch/xpack/esql/parser/EsqlBaseParser*.java",
-        "src/main/java/generated/**/*.java"
+        "src/main/generated/**/*.java",
+        "src/main/generated-src/generated/**/*.java"
     }
   }
 }
@@ -250,6 +238,8 @@ tasks.register("regen") {
 tasks.named("spotlessJava") { dependsOn stringTemplates }
 tasks.named('checkstyleMain').configure {
   excludes = [ "**/*.java.st" ]
+  exclude { it.file.toString().startsWith("${projectDir}/src/main/generated-src/generated") }
+  exclude { it.file.toString().startsWith("${projectDir}/src/main/generated") }
 }
 
 def prop(Type, type, TYPE, BYTES, Array) {