[SPARK-3873] [build] Add scalastyle checker for import ordering.

Currently generates only warnings, since there are many violations.
dev/scalastyle was modified to not get rid of the output file, since
that contains the list of warnigs which could help with cleaning
things up.

dev/scalastyle

@@ -24,7 +24,9 @@ echo -e "q\n" | build/sbt -Pkinesis-asl -Pyarn -Phadoop-2.2 scalastyle >> scalas
 echo -e "q\n" | build/sbt -Pkinesis-asl -Pyarn -Phadoop-2.2 test:scalastyle >> scalastyle.txt
 
 ERRORS=$(cat scalastyle.txt | awk '{if($1~/error/)print}')
-rm scalastyle.txt
+mkdir -p target
+rm -f target/scalastyle.txt
+mv scalastyle.txt target/
 
 if test ! -z "$ERRORS"; then
     echo -e "Scalastyle checks failed at following occurrences:\n$ERRORS"

pom.xml

@@ -2235,7 +2235,7 @@
       <plugin>
         <groupId>org.scalastyle</groupId>
         <artifactId>scalastyle-maven-plugin</artifactId>
-        <version>0.7.0</version>
+        <version>0.8.0</version>
         <configuration>
           <verbose>false</verbose>
           <failOnViolation>true</failOnViolation>

project/plugins.sbt

@@ -17,7 +17,7 @@ addSbtPlugin("com.github.mpeltonen" % "sbt-idea" % "1.6.0")
 
 addSbtPlugin("net.virtual-void" % "sbt-dependency-graph" % "0.7.4")
 
-addSbtPlugin("org.scalastyle" %% "scalastyle-sbt-plugin" % "0.7.0")
+addSbtPlugin("org.scalastyle" %% "scalastyle-sbt-plugin" % "0.8.0")
 
 addSbtPlugin("com.typesafe" % "sbt-mima-plugin" % "0.1.6")
 

scalastyle-config.xml

@@ -203,6 +203,18 @@ This file is divided into 3 sections:
   <!-- Should turn this on, but we have a few places that need to be fixed first -->
   <check level="error" class="org.scalastyle.scalariform.EqualsHashCodeChecker" enabled="false"></check>
 
+  <!-- Import ordering. Currently warning only since there are lots of violations. -->
+  <check level="warning" class="org.scalastyle.scalariform.ImportOrderChecker" enabled="true">
+    <parameters>
+      <parameter name="groups">java,scala,3rdParty,spark</parameter>
+      <parameter name="group.java">javax?\..+</parameter>
+      <parameter name="group.scala">scala\..+</parameter>
+      <parameter name="group.3rdParty">(?!org\.apache\.spark\.).*</parameter>
+      <parameter name="group.spark">org\.apache\.spark\..*</parameter>
+    </parameters>
+  </check>
+
+
   <!-- ================================================================================ -->
   <!--                               rules we don't want                                -->
   <!-- ================================================================================ -->