txn: Add RangedKVRetriever struct to provide custom range data operations

[lcwangchao]

What problem does this PR solve?

Issue Number: close #27541

Problem Summary:

see #26952

To make a better implement for temporary table. It is required that snapshot can read data from other sources like memory for some specified ranges. So we expect snapshot can provide some methods to override data fetch.

What is changed and how it works?

draft is here tikv/client-go#262 . Because it is not a universal demand, so move it to tidb。

Check List

Tests

• Unit test

Release note

None

[ti-chi-bot]

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• disksing
• tiancaiamao

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[lcwangchao]

/run-check_dev_2

[tiancaiamao]

I'll take a look tomorrow

[ti-chi-bot]

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[disksing]

/rebuild

[disksing]

/approve

[disksing]

LGTM

[disksing]

/lgtm

[lcwangchao]

/run-all-tests

[disksing]

/merge

[ti-chi-bot]

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

Commit hash: 343560b