Compat serverless FAP features including shard_ver, txn ref and enc key

[CalvinNeo]

What problem does this PR solve?

Issue Number: ref #8673

Problem Summary:

Ref https://github.com/tidbcloud/tiflash-cse/pull/287.

We have to add some dummy implementations in TiFlash master, to reduce the divergence between serverless interfaces and codes.

The PR includes:

1. In Proxy, we update ProxyFFI.h for some changes. We also introduce a serverless_extra.rs file that does nothing as a stub file.
2. In TiFlash, we add and change some functions in FastAddPeer.cpp to support newly added interfaces. The newly add functions will always return empty(string or int). So there is little side effect.

What is changed and how it works?

Compatibility for serverless FAP features including shard_ver, txn ref and enc key

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

None

[JaySon-Huang]

Generally LGTM

The changes in tiflash-proxy should be a formal commit on the raftstore-proxy branch?

[CalvinNeo]

Generally LGTM

The changes in tiflash-proxy should be a formal commit on the raftstore-proxy branch?

Yes, Hold this PR until proxy's PR is merged

[CalvinNeo]

/unhold

[JaySon-Huang]

LGTM

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: JaySon-Huang, Lloyd-Pottiger

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[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2024-09-20 07:17:39.480877149 +0000 UTC m=+1204729.221301104: ☑️ agreed by JaySon-Huang.
• 2024-09-20 07:35:35.194789972 +0000 UTC m=+1205804.935213895: ☑️ agreed by Lloyd-Pottiger.