tso: refine the codes of TSO and TSO tests

[JmPotato]

Signed-off-by: JmPotato [email protected]

What problem does this PR solve?

Refine the codes of TSO and TSO tests.

What is changed and how it works?

• Add and merge some common methods.
• Refine the codes.
• Add and adjust some comments.

Check List

Tests

• Unit test
• Integration test

Release note

[codecov]

Codecov Report

Merging #3290 (935c59c) into master (38a764b) will increase coverage by 0.20%.
The diff coverage is 77.55%.

@@            Coverage Diff             @@
##           master    #3290      +/-   ##
==========================================
+ Coverage   74.62%   74.83%   +0.20%     
==========================================
  Files         243      243              
  Lines       23192    23207      +15     
==========================================
+ Hits        17308    17366      +58     
+ Misses       4308     4270      -38     
+ Partials     1576     1571       -5     

Flag	Coverage Δ
unittests	74.83% <77.55%> (+0.20%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
server/tso/global_allocator.go	64.56% <37.50%> (+1.86%)	⬆️
server/tso/allocator_manager.go	75.85% <93.33%> (-1.15%)	⬇️
pkg/etcdutil/etcdutil.go	84.70% <100.00%> (-0.59%)	⬇️
server/tso/tso.go	80.50% <100.00%> (+0.62%)	⬆️
pkg/dashboard/adapter/manager.go	81.52% <0.00%> (-7.61%)	⬇️
pkg/btree/btree.go	85.30% <0.00%> (-0.97%)	⬇️
client/client.go	65.67% <0.00%> (+0.37%)	⬆️
server/server.go	73.29% <0.00%> (+0.47%)	⬆️
... and 12 more

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[JmPotato]

/run-build-image

[Yisaer]

Rest LGTM

[Yisaer]

LGTM

[nolouch]

/merge

[ti-chi-bot]

@nolouch: It seems you want to merge this PR, I will help you trigger all the tests:

/run-all-tests

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the ti-community-infra/ti-community-prow repository.

[ti-chi-bot]

This pull request has been accepted and is ready to merge.

Commit hash: 935c59c