[close #350] Fix flaky it http_api

[pingyu]

What problem does this PR solve?

Issue Number: close #issue_number

Problem Description: TBD

What is changed and how does it work?

The issus seems to be caused by tikv-server OOM killed.

Reduce memory usage by specify small capacity of block cache and reduce number of tikv-server instantce.

Code changes

• No code

Check List for Tests

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

• Integration test

Side effects

• 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

To reviewers

Please follow these principles to check this pull requests:

• Concentration. One pull request should only do one thing. No matter how small it is, the change does exactly one thing and gets it right. Don't mix other changes into it.
• Tests. A pull request should be test covered, whether the tests are unit tests, integration tests, or end-to-end tests. Tests should be sufficient, correct and don't slow down the CI pipeline largely.
• Functionality. The pull request should implement what the author intends to do and fit well in the existing code base, resolve a real problem for TiDB/TiKV users. To get the author's intention and the pull request design, you could follow the discussions in the corresponding GitHub issue or internal.tidb.io topic.
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[codecov]

Codecov Report

Merging #351 (ba225c0) into main (c340278) will increase coverage by 0.1699%.
Report is 1 commits behind head on main.
The diff coverage is 63.7500%.

Additional details and impacted files

@@               Coverage Diff                @@
##               main       #351        +/-   ##
================================================
+ Coverage   61.1272%   61.2972%   +0.1699%     
================================================
  Files           240        241         +1     
  Lines         20261      20412       +151     
================================================
+ Hits          12385      12512       +127     
- Misses         6758       6759         +1     
- Partials       1118       1141        +23     

Flag	Coverage Δ		*Carryforward flag
br	60.6802% <ø> (ø)		Carriedforward from e46a07a
cdc	61.5796% <63.7500%> (+0.2455%)	⬆️

*This pull request uses carry forward flags. Click here to find out more.

Files Changed	Coverage Δ
cdc/cdc/kv/metrics.go	0.0000% <0.0000%> (ø)
cdc/cdc/processor/pipeline/keyspan.go	0.0000% <0.0000%> (ø)
cdc/cdc/processor/pipeline/puller.go	0.0000% <0.0000%> (ø)
cdc/pkg/config/replica_config.go	63.2653% <0.0000%> (-5.6236%)	⬇️
cdc/pkg/util/ctx.go	76.4705% <0.0000%> (-12.1658%)	⬇️
cdc/cdc/kv/region_worker.go	78.6885% <33.3333%> (-0.8949%)	⬇️
cdc/pkg/cmd/cli/cli_changefeed_update.go	28.2051% <66.6666%> (+2.9877%)	⬆️
cdc/pkg/util/kv_filter.go	91.6666% <91.6666%> (ø)
cdc/cdc/kv/client.go	83.8848% <100.0000%> (-2.1382%)	⬇️

... and 15 files with indirect coverage changes

[pingyu]

/run-integration-test

[pingyu]

/run-integration-test

[pingyu]

/run-integration-test

[zeminzhou]

LGTM～