ddl: support alter index for multi-schema change

[tangenta]

What problem does this PR solve?

Issue Number: ref #14766

Problem Summary:

This PR supports alter multiple indexes in one DDL statement.

What is changed and how it works?

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

Please refer to Release Notes Language Style Guide to write a quality release note.

None

[ti-chi-bot]

[REVIEW NOTIFICATION]

This pull request has been approved by:

• wjhuang2016
• zimulala

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[zimulala]

LGTM

[tangenta]

/merge

[ti-chi-bot]

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

Commit hash: 83a4d3b

[hawkingrei]

@tangenta

    tiflash_replica_test.go:189: 
        	Error Trace:	tiflash_replica_test.go:189
        	Error:      	Not equal: 
        	            	expected: "[ddl:8200]ALTER table replica for tables in system database is currently unsupported"
        	            	actual  : "[planner:1142]ALTER command denied to user 'root'@'%' for table 'advisory_locks'"
        	            	
        	            	Diff:
        	            	--- Expected
        	            	+++ Actual
        	            	@@ -1 +1 @@
        	            	-[ddl:8200]ALTER table replica for tables in system database is currently unsupported
        	            	+[planner:1142]ALTER command denied to user 'root'@'%' for table 'advisory_locks'
        	Test:       	TestSetTableFlashReplicaForSystemTable

[hawkingrei]

/hold

[tangenta]

-[ddl:8200]ALTER table replica for tables in system database is currently unsupported
+[planner:1142]ALTER command denied to user 'root'@'%' for table 'advisory_locks'
        	Test:       	TestSetTableFlashReplicaForSystemTable
        	Messages:   	sem enabled: true

I don't understand why the SEM is enabled after this PR.

[tangenta]

/merge

[ti-chi-bot]

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

Commit hash: 925b1be

[sre-bot]

Code Coverage Details: https://codecov.io/github/pingcap/tidb/commit/d4984adf6622bdc97a7a38d3019de30abdf2a574

[tangenta]

/unhold

[ti-chi-bot]

@tangenta: 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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