integration_tests(ticdc): move integration tests into integration_tests dir (#3646)

[ti-chi-bot]

This is an automated cherry-pick of #3646

What problem does this PR solve?

part of https://github.com/pingcap/ticdc/issues/2199

What is changed and how it works?

move integration tests into integration_tests dir.
Other test-related files will be moved to this directory later.

Check List

Tests

• Integration test

Code changes

None

Side effects

None

Related changes

• Need to cherry-pick to the release branch

Release note

None

[ti-chi-bot]

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[Rustin170506]

/run-all-tests

[codecov-commenter]

Codecov Report

❗ No coverage uploaded for pull request base (release-5.1@bedd0fb). Click here to learn what that means.
The diff coverage is n/a.

@@               Coverage Diff                @@
##             release-5.1      #3690   +/-   ##
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  Coverage               ?   57.6846%           
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  Files                  ?        165           
  Lines                  ?      19461           
  Branches               ?          0           
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  Hits                   ?      11226           
  Misses                 ?       7180           
  Partials               ?       1055           

[Rustin170506]

/run-all-tests

[amyangfei]

/merge

[ti-chi-bot]

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

Commit hash: fccb038