sorter: remove file sorter (#2114)

[ti-chi-bot]

This is an automated cherry-pick of #2114

What problem does this PR solve?

• File sorter has not been maintained and tested for a long time, and no one we know of uses it in production.

What is changed and how it works?

• Removed file sorter.
• For compatibility of running changefeeds, we use Unified Sorter in place when the user has previously set sort-engine to file.
• The CLI will refuse the set sort-engine to file.

Check List

Tests

• Integration test

Side effects

• Breaking backward compatibility

Related changes

• Need to cherry-pick to the release branch
• Need to update the documentation

Release note

• Remove file sorter.

[ti-chi-bot]

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[amyangfei]

/merge

[ti-chi-bot]

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

Commit hash: 2f78855

[amyangfei]

/run-all-tests

[amyangfei]

/run-integration-tests

[amyangfei]

/run-integration-tests
/run-kafka-tests

[ti-chi-bot]

@ti-chi-bot: Your PR was out of date, I have automatically updated it for you.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

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[amyangfei]

/run-integration-tests