ESQL: Disable format checks on generated imports

This builds the infrastructure to disable spotless and some checkstyle
rules on generated imports. This works around the most frustrating part
of ESQL's string template generated files - the imports. It allows
unused and out of order imports. This can let us remove a lot of
cumbersome, tricky, and fairly useless `$if$` blocks from the templates.

Author: nik9000

build-tools-internal/src/main/resources/checkstyle.xml

@@ -68,6 +68,11 @@
 
     <!-- Unused imports are forbidden -->
     <module name="UnusedImports" />
+    <module name="SuppressionCommentFilter">
+      <property name="offCommentFormat" value="begin generated imports"/>
+      <property name="onCommentFormat" value="end generated imports"/>
+      <property name="checkFormat" value="UnusedImports"/>
+    </module>
 
     <!-- Non-inner classes must be in files that match their names. -->
     <module name="OuterTypeFilename" />

x-pack/plugin/esql/compute/build.gradle

@@ -49,6 +49,7 @@ spotless {
     /*
      * Generated files go here.
      */
+    toggleOffOn('begin generated imports', 'end generated imports')
     targetExclude "src/main/generated/**/*.java"
   }
 }

x-pack/plugin/esql/compute/src/main/generated-src/org/elasticsearch/compute/data/BooleanArrayVector.java

@@ -7,7 +7,7 @@
 
 package org.elasticsearch.compute.data;
 
-$if(BytesRef)$
+// begin generated imports
 import org.apache.lucene.util.BytesRef;
 import org.apache.lucene.util.RamUsageEstimator;
 import org.elasticsearch.common.io.stream.StreamInput;
@@ -17,19 +17,10 @@ import org.elasticsearch.common.util.BytesRefArray;
 import org.elasticsearch.core.ReleasableIterator;
 import org.elasticsearch.core.Releasables;
 
-import java.io.IOException;
-
-$else$
-import org.apache.lucene.util.RamUsageEstimator;
-import org.elasticsearch.common.io.stream.StreamInput;
-import org.elasticsearch.common.io.stream.StreamOutput;
-import org.elasticsearch.common.unit.ByteSizeValue;
-import org.elasticsearch.core.ReleasableIterator;
-
 import java.io.IOException;
 import java.util.stream.Collectors;
 import java.util.stream.IntStream;
-$endif$
+// end generated imports
 
 /**
  * Vector implementation that stores an array of $type$ values.