Refactor Charset using and blob utils.

[ujjboy]

Ⅰ. Describe what this PR did

• All use default UTF-8 charset
• Remove BlobUtils#inputStream2String() which duplicate with StringUtils
• Delete StringUtils#string2blob() which duplicate with BlobUtils
• Add BlobUtils#blob2Bytes() and BlobUtils#bytes2Blob()
• Add more test case.

[codecov-io]

Codecov Report

Merging #1084 into develop will increase coverage by 0.18%.
The diff coverage is 77.41%.

@@              Coverage Diff              @@
##             develop    #1084      +/-   ##
=============================================
+ Coverage      39.94%   40.13%   +0.18%     
- Complexity      1153     1163      +10     
=============================================
  Files            222      222              
  Lines           8929     8940      +11     
  Branches        1158     1158              
=============================================
+ Hits            3567     3588      +21     
+ Misses          4914     4907       -7     
+ Partials         448      445       -3

Impacted Files	Coverage Δ	Complexity Δ
...va/io/seata/rm/datasource/undo/UndoLogManager.java	23.22% <0%> (ø)	8 <0> (ø)	⬇️
...n/java/io/seata/core/protocol/AbstractMessage.java	15.51% <100%> (ø)	5 <1> (ø)	⬇️
...ommon/src/main/java/io/seata/common/Constants.java	50% <100%> (+50%)	1 <1> (+1)	⬆️
.../io/seata/common/loader/EnhancedServiceLoader.java	68.86% <100%> (ø)	23 <0> (ø)	⬇️
...rc/main/java/io/seata/common/util/StringUtils.java	24.05% <76.47%> (+11.55%)	13 <6> (+3)	⬆️
.../src/main/java/io/seata/common/util/BlobUtils.java	60% <80%> (+48.23%)	8 <4> (+6)	⬆️

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[xingfudeshi]

LGTM