parse diskPartsKey and add unit test

[Nivras]

What type of PR is this?

• bug
• feature
• enhancement

What does this PR do?

add functions to parse host, spaceId and path in diskPartsKey, and fix parseDiskPartsSpace().
add unit test for MetaUtilKeys and DiskManager

Which issue(s)/PR(s) this PR relates to?

#3369

Special notes for your reviewer, ex. impact of this fix, etc:

Additional context:

Checklist：

• Documentation affected （Please add the label if documentation needs to be modified.)
• Incompatible （If it is incompatible, please describe it and add corresponding label.）
• Need to cherry-pick （If need to cherry-pick to some branches, please label the destination version(s).)
• Performance impacted: Consumes more CPU/Memory

Release notes：

Please confirm whether to reflect in release notes and how to describe:

                                                            `

[critical27]

Well done

[codecov-commenter]

Codecov Report

Merging #3416 (1421f30) into master (d6f83f3) will increase coverage by 0.02%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #3416      +/-   ##
==========================================
+ Coverage   85.24%   85.26%   +0.02%     
==========================================
  Files        1278     1278              
  Lines      119200   119254      +54     
==========================================
+ Hits       101608   101684      +76     
+ Misses      17592    17570      -22     

Impacted Files	Coverage Δ
src/common/memory/MemoryUtils.cpp	93.33% <100.00%> (+0.65%)	⬆️
src/common/utils/MetaKeyUtils.cpp	82.15% <100.00%> (+0.78%)	⬆️
src/common/utils/test/MetaKeyUtilsTest.cpp	94.63% <100.00%> (+0.30%)	⬆️
src/kvstore/test/DiskManagerTest.cpp	99.19% <100.00%> (+0.21%)	⬆️
src/meta/processors/BaseProcessor.h	75.67% <0.00%> (-16.22%)	⬇️
...c/meta/processors/parts/GetPartsAllocProcessor.cpp	83.05% <0.00%> (-8.48%)	⬇️
src/common/thrift/ThriftClientManager-inl.h	82.97% <0.00%> (-6.39%)	⬇️
src/graph/planner/Planner.cpp	75.00% <0.00%> (-5.00%)	⬇️
src/graph/service/PermissionCheck.cpp	78.72% <0.00%> (-2.13%)	⬇️
src/codec/RowReaderWrapper.h	94.23% <0.00%> (-1.93%)	⬇️
... and 23 more

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[pengweisong]

Good job. LGTM.