*: add create time to admin show ddl jobs

[wjhuang2016]

What problem does this PR solve?

Issue Number: ref #23494, ref PR #24151

Problem Summary:
We want to know the create time and the start time of a DDL job.

What is changed and how it works?

Add a column create time, which is the previous start time.
And the column start time will be the real start time.

Check List

Tests

• Unit test
• Integration test
• Manual test (add detailed scripts or steps below)

• No code

Side effects

• Performance regression: Consumes more CPU
• Performance regression: Consumes more Memory
• Breaking backward compatibility

Documentation

• Affects user behaviors
• Contains syntax changes
• Contains variable changes
• Contains experimental features
• Changes MySQL compatibility

Release note

add create time to `admin show ddl jobs`

[ti-chi-bot]

[REVIEW NOTIFICATION]

This pull request has been approved by:

• tangenta
• zimulala

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[hawkingrei]

/run-unit-test

[hawkingrei]

[2022-02-17T09:49:59.183Z] FAIL: executor_test.go:538: testSuiteP2.TestAdminShowDDLJobs

[2022-02-17T09:49:59.183Z] 

[2022-02-17T09:49:59.183Z] executor_test.go:572:

[2022-02-17T09:49:59.183Z]     c.Assert(row[9], Equals, "<nil>")

[2022-02-17T09:49:59.183Z] ... obtained string = "2022-02-17 17:49:53"

[2022-02-17T09:49:59.183Z] ... expected string = "<nil>"

Please fix it.

[zimulala]

LGTM

[sre-bot]

Code Coverage Details: https://codecov.io/github/pingcap/tidb/commit/2936eebe304285ba0d9040aba8cd968c25907201

[hawkingrei]

/run-mysql-test

[wjhuang2016]

/merge

[ti-chi-bot]

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

Commit hash: ab8a871

[ti-chi-bot]

@wjhuang2016: Your PR was out of date, I have automatically updated it for you.

At the same time I will also trigger all tests for you:

/run-all-tests

If the CI test fails, you just re-trigger the test that failed and the bot will merge the PR for you after the CI passes.

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[hawkingrei]

/run-unit-test