refactor: make active_chain_tip a reference

[aureleoules]

This PR fixes a TODO introduced in #21055.

Makes active_chain_tip argument in CheckFinalTxAtTip function a reference instead of a pointer.

[DrahtBot]

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Conflicts

Reviewers, this pull request conflicts with the following ones:

• #25073 (test: Cleanup miner_tests by MarcoFalke)
• #23897 (refactor: Move calculation logic out from CheckSequenceLocksAtTip() by hebasto)

If you consider this pull request important, please also help to review the conflicting pull requests. Ideally, start with the one that should be merged first.

[fanquake]

cc @MarcoFalke @dongcarl re #20750 (comment).

[dongcarl]

ACK 9376a6d

I'm guessing cuz the reference is const it's getting lifetime extension?

[maflcko]

I'm guessing cuz the reference is const it's getting lifetime extension?

I don't think any lifetimes change here, as passing a reference as a parameter is lifetime-wise identical to passing a pointer. Also, lifetimes shouldn't matter here, as the function does not return the reference/pointer or otherwise stores it in memory that survives past the return of the function.

If you are asking whether a temporary can now be passed into the function: Then yes, this is now possible and legal C++ code. However for the purposes of our validation code creating a temporary is just as illegal as creating a copy, see #25311.