TiStore: add implement Serializable

[liangyouze]

What problem does this PR solve?

When I use it in Tispark, the following exception will be thrown

Caused by: java.io.NotSerializableException: org.tikv.common.region.TiStore
Serialization stack:
	- object not serializable (class: org.tikv.common.region.TiStore, value: org.tikv.common.region.TiStore@1f547af8)
	- writeObject data (class: java.util.ArrayList)
	- object (class java.util.ArrayList, [org.tikv.common.region.TiStore@1f547af8, org.tikv.common.region.TiStore@701c482e, org.tikv.common.region.TiStore@4738131e])
	- field (class: org.tikv.common.region.TiRegion, name: stores, type: interface java.util.List)
	- object (class org.tikv.common.region.TiRegion, {Region[2009] ConfVer[5] Version[8] Store[4] KeyRange[]:[bNmuyJQt]})
	- writeObject data (class: scala.collection.immutable.List$SerializationProxy)
	- object (class scala.collection.immutable.List$SerializationProxy, scala.collection.immutable.List$SerializationProxy@416d90f0)
	- writeReplace data (class: scala.collection.immutable.List$SerializationProxy)
	- object (class scala.collection.immutable.$colon$colon, List({Region[2009] ConfVer[5] Version[8] Store[4] KeyRange[]:[bNmuyJQt]}, {Region[2] ConfVer[5] Version[8] Store[1] KeyRange[bNmuyJQt]:[]}))
	- field (class: org.apache.spark.rawkvbulkload.TiReginSplitPartitionerV2, name: orderedRegions, type: class scala.collection.immutable.List)
	- object (class org.apache.spark.rawkvbulkload.TiReginSplitPartitionerV2, org.apache.spark.rawkvbulkload.TiReginSplitPartitionerV2@3c98981e)
	- field (class: org.apache.spark.rawkvbulkload.RawKVBulkLoad, name: partitioner, type: class org.apache.spark.rawkvbulkload.TiReginSplitPartitionerV2)
	- object (class org.apache.spark.rawkvbulkload.RawKVBulkLoad, org.apache.spark.rawkvbulkload.RawKVBulkLoad@6a38e3d1)
	- element of array (index: 0)
	- array (class [Ljava.lang.Object;, size 1)
	- field (class: java.lang.invoke.SerializedLambda, name: capturedArgs, type: class [Ljava.lang.Object;)
	- object (class java.lang.invoke.SerializedLambda, SerializedLambda[capturingClass=class org.apache.spark.rawkvbulkload.RawKVBulkLoad, functionalInterfaceMethod=scala/Function1.apply:(Ljava/lang/Object;)Ljava/lang/Object;, implementation=invokeStatic org/apache/spark/rawkvbulkload/RawKVBulkLoad.$anonfun$bulkLoad$5$adapted:(Lorg/apache/spark/rawkvbulkload/RawKVBulkLoad;Lscala/collection/Iterator;)Ljava/lang/Object;, instantiatedMethodType=(Lscala/collection/Iterator;)Ljava/lang/Object;, numCaptured=1])
	- writeReplace data (class: java.lang.invoke.SerializedLambda)
	- object (class org.apache.spark.rawkvbulkload.RawKVBulkLoad$$Lambda$2335/456897159, org.apache.spark.rawkvbulkload.RawKVBulkLoad$$Lambda$2335/456897159@7dd7ec56)
	at org.apache.spark.serializer.SerializationDebugger$.improveException(SerializationDebugger.scala:41)
	at org.apache.spark.serializer.JavaSerializationStream.writeObject(JavaSerializer.scala:47)
	at org.apache.spark.serializer.JavaSerializerInstance.serialize(JavaSerializer.scala:101)
	at org.apache.spark.util.ClosureCleaner$.ensureSerializable(ClosureCleaner.scala:413)
	... 23 more

What is changed and how it works?

The Class TiStore should implement Serializable

Check List

Tests

• Unit test
• Integration test
• Manual test (add detailed scripts or steps below)
• No code

Code changes

• Has exported function/method change
• Has exported variable/fields change
• Has interface methods change
• Has persistent data change

Side effects

• Possible performance regression
• Increased code complexity
• Breaking backward compatibility

Related changes

• Need to cherry-pick to the release branch
• Need to update the documentation
• Need to be included in the release note

[marsishandsome]

please add sign-off

[marsishandsome]

/run-all-tests

[marsishandsome]

LGTM

[marsishandsome]

/merge

[ti-srebot]

/run-all-tests

[ti-srebot]

@liangyouze merge failed.

[marsishandsome]

/run-all-tests