infoschema, session: support for events_statements_summary_by_digest #12017

[djshow832]

cherry-pick #12017 to release-3.0, with little conflict-resolve

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What problem does this PR solve?

Support system table events_statements_summary_by_digest, which is used to summary statements by digest.

What is changed and how it works?

• Add methods to perfSchemaTable, and add a new table events_statements_summary_by_digest.
• Add a system variable tidb_enable_stmt_summary and add configurations max-stmt-count & max-sql-length.
• Summary the statement execution information and put it into StmtSummary after a SQL runs.
• Get information from StmtSummary when the user queries events_statements_summary_by_digest.

Check List

Tests

• Unit test

Code changes

• Has exported function/method change
• Has exported variable/fields change
• Has interface methods change

Side effects

• Possible performance regression
• Increased code complexity

Related changes

• Need to cherry-pick to the release branch

Release note

• Support system table performance_schema.events_statements_summary_by_digest. The table is used to summarize statements by digest of statements.

[coocood]

LGTM

[bb7133]

LGTM

[sre-bot]

/run-all-tests