[close #693] Add test for RangeSplitter

[shiyuhang0]

Signed-off-by: shiyuhang 1136742008@qq.com

What problem does this PR solve?

Issue Number: close #693
Problem Description: Add test for RangeSplitter

What is changed and how does it work?

Add test for RangeSplitter. reference: https://github.com/pingcap/tispark/blob/release-3.1/tikv-client/src/test/java/com/pingcap/tikv/util/RangeSplitterTest.java

Code changes

• Has exported function/method change
• Has exported variable/fields change
• Has methods of interface change
• Has persistent data change
• No code

Check List for Tests

This PR has been tested by at least one of the following methods:

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

Side effects

• Possible performance regression, WHY: TBD
• Increased code complexity, WHY: TBD
• Breaking backward compatibility, WHY: TBD
• NO side effects

Related changes

• Need to cherry-pick to the release branch
• Need to update the documentation
• Need to be included in the release note
• NO related changes

[codecov]

Codecov Report

Base: 37.19% // Head: 37.97% // Increases project coverage by +0.77% 🎉

Coverage data is based on head (6eb836f) compared to base (a459a6e).
Patch has no changes to coverable lines.

Additional details and impacted files

@@             Coverage Diff              @@
##             master     #694      +/-   ##
============================================
+ Coverage     37.19%   37.97%   +0.77%     
- Complexity     1565     1597      +32     
============================================
  Files           278      278              
  Lines         17386    17386              
  Branches       1978     1978              
============================================
+ Hits           6467     6602     +135     
+ Misses        10268    10124     -144     
- Partials        651      660       +9     

Impacted Files	Coverage Δ
...rc/main/java/io/grpc/netty/NettyClientHandler.java	56.03% <0.00%> (-0.22%)	⬇️
src/main/java/io/grpc/internal/ClientCallImpl.java	56.82% <0.00%> (+0.48%)	⬆️
src/main/java/org/tikv/common/TiConfiguration.java	71.59% <0.00%> (+0.76%)	⬆️
...ty/handler/codec/http2/Http2ConnectionHandler.java	49.87% <0.00%> (+1.71%)	⬆️
.../main/java/org/tikv/common/util/KeyRangeUtils.java	4.16% <0.00%> (+2.08%)	⬆️
...va/org/tikv/common/region/StoreHealthyChecker.java	73.41% <0.00%> (+3.79%)	⬆️
src/main/java/org/tikv/common/key/RowKey.java	41.50% <0.00%> (+41.50%)	⬆️
.../main/java/org/tikv/common/util/RangeSplitter.java	82.90% <0.00%> (+82.90%)	⬆️

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[ti-srebot]

cherry pick to release-3.3 in PR #698