id: fix the id allocator is not monotonic (#3305)

[ti-srebot]

cherry-pick #3305 to release-3.0

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What problem does this PR solve?

What is changed and how it works?

This PR tries to make the id monotonic since there are many components that depend on this property. ref: #3303

Check List

Tests

• Unit test

Related changes

• PR to update pingcap/docs/pingcap/docs-cn:
• PR to update pingcap/tidb-ansible:
• Need to cherry-pick to the release branch

Release note

[ti-srebot]

@rleungx you're already a collaborator in bot's repo.

[lhy1024]

plz fix

[HunDunDM]

This PR contains #3310

[codecov]

Codecov Report

Merging #3309 (7c5a39e) into release-3.0 (669ecba) will decrease coverage by 0.14%.
The diff coverage is 53.33%.

@@               Coverage Diff               @@
##           release-3.0    #3309      +/-   ##
===============================================
- Coverage        67.35%   67.20%   -0.15%     
===============================================
  Files              171      170       -1     
  Lines            14334    14315      -19     
===============================================
- Hits              9654     9621      -33     
- Misses            3740     3746       +6     
- Partials           940      948       +8     

Impacted Files	Coverage Δ
server/leader.go	76.49% <33.33%> (-0.61%)	⬇️
server/id.go	72.97% <54.54%> (+1.54%)	⬆️
server/server.go	78.20% <100.00%> (+0.05%)	⬆️
pkg/etcdutil/etcdutil.go	86.11% <0.00%> (-8.34%)	⬇️
server/namespace_cluster.go	81.48% <0.00%> (-5.56%)	⬇️
server/util.go	65.67% <0.00%> (-5.23%)	⬇️
server/tso.go	74.41% <0.00%> (-4.66%)	⬇️
server/grpc_service.go	56.35% <0.00%> (-1.85%)	⬇️
client/client.go	68.94% <0.00%> (-1.42%)	⬇️
server/handler.go	45.88% <0.00%> (-0.59%)	⬇️
... and 10 more

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[rleungx]

/run-all-tests

[rleungx]

/run-integration-lightning-test

[nolouch]

/run-integration-lightning-test

[nolouch]

/run-integration-ddl-test

[nolouch]

contains #3322.