fuzz: Improve fuzzing stability for txorphan harness

[dergoegge]

The txorphan harness has low stability as eviction of orphan txs is entirely random at the moment.

Fix this by passing the rng to LimitOrphans, which can be deterministic in tests.

Also see #29018.

[DrahtBot]

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Type	Reviewers
ACK	maflcko, brunoerg

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Conflicts

Reviewers, this pull request conflicts with the following ones:

• #28970 ([WIP] p2p: opportunistically accept 1-parent-1-child packages by glozow)

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[brunoerg]

Concept ACK

nice!

[maflcko]

lgtm ACK 15f5a0d

Didn't test the stability score.

[dergoegge]

Didn't test the stability score.

I'm seeing 87% stability locally, up from 51% reported by oss-fuzz. Not sure why it isn't a 100%, can't see anything else in the orphanage that would be non-deterministic.

[brunoerg]

utACK 15f5a0d

[glozow]

concept ACK 15f5a0d