fix row key not in standard format (#7901)

[ti-chi-bot]

This is an automated cherry-pick of #7901

What problem does this PR solve?

Issue Number: close #3099 close #7762

Problem Summary: For int handle, the standard row key format should be t{tidb_id}_r{row_id}, but the cluster may generate keys not strictly adhere to this format. For example, it may append a 0x00 to the encoded value.
When tiflash decode the key, it will ignore the suffix 0x00 and may get an invalid row key value.

What is changed and how it works?

For row key which size is larger than the standard format, we add 1 on the decoded int key value.
This is ok, because

1. if the key is the start range, then [t100_r1000 + 0x00, xxx) has the same semantics with [t100_r1001, xxx)
2. if the key is the end range, then [xxx, t100_r1000 + 0x00) also has the same semantics with [xxx, t100_r1001)

Note if the decoded int value is Int64::max_value, it is a value generated by tiflash itself which is RowKeyValue::INT_HANDLE_MAX_KEY. This is a special key to means +inf, so we can just ignore it.

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

Fix the potential consistency problem when the int type row key value is not in standard encoding format

[ti-chi-bot]

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[ti-chi-bot]

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