*: fix the order of FallbackOldAndSetNewAction

[YangKeao]

Signed-off-by: YangKeao yangkeao@chunibyo.icu

What problem does this PR solve?

Issue Number: close #37058

Problem Summary:

1. The order of FallbackOldAndSetNewAction is wrong. It should set the current action to the new one, and set the original one as its fallback (as how it's used, and described in the comments). However, it acts in the opposite way now 🤦 , and cause the unstable test.
2. The bytes limit of the third test is too low, which may cause two partitions. I increased the bytes limit, and it will only spill one partition now.

What is changed and how it works?

I rearrange the arguments order of the FallbackOldAndSetNewAction

Check List

Tests

• Unit test
• [ ]Integration test
• Manual test
• No code

I manually, repeatedly run this test multiple times (in parallel, 32 jobs) for several minutes, and it seems that it's stable now ❤️ .

Release note

Fix the issue that the action order of 

[ti-chi-bot]

[REVIEW NOTIFICATION]

This pull request has been approved by:

• tiancaiamao
• xhebox

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[ti-chi-bot]

Code Coverage Details: https://codecov.io/github/pingcap/tidb/commit/3c535ef3bc7901fea3cd2fd9d2d98172fb12b31c

[hawkingrei]

/merge

[ti-chi-bot]

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

Commit hash: 89ed0e9

[hawkingrei]

/run-mysql-test tidb-test=pr/1937

[sre-bot]

TiDB MergeCI notify

🔴 Bad News! [2] CI still failing after this pr merged.
These failed integration tests don't seem to be introduced by the current PR.

CI Name	Result	Duration	Compare with Parent commit
idc-jenkins-ci-tidb/integration-common-test	🔴 failed 4, success 13, total 17	15 min	Existing failure
idc-jenkins-ci-tidb/common-test	🔴 failed 1, success 10, total 11	12 min	Existing failure
idc-jenkins-ci/integration-cdc-test	🟢 all 36 tests passed	27 min	Existing passed
idc-jenkins-ci-tidb/integration-ddl-test	🟢 all 6 tests passed	6 min 23 sec	Existing passed
idc-jenkins-ci-tidb/sqllogic-test-1	🟢 all 26 tests passed	6 min 12 sec	Existing passed
idc-jenkins-ci-tidb/sqllogic-test-2	🟢 all 28 tests passed	6 min 3 sec	Existing passed
idc-jenkins-ci-tidb/tics-test	🟢 all 1 tests passed	5 min 32 sec	Existing passed
idc-jenkins-ci-tidb/mybatis-test	🟢 all 1 tests passed	3 min 35 sec	Existing passed
idc-jenkins-ci-tidb/integration-compatibility-test	🟢 all 1 tests passed	3 min 4 sec	Existing passed
idc-jenkins-ci-tidb/plugin-test	🟢 build success, plugin test success	4min	Existing passed