Fix EnvelopeMapper swapped filter predicates breaking single-direction property overrides (#2551)

[jeremydmiller]

Fixes #2551.

The bug

EnvelopeMapper<TIncoming, TOutgoing> had its compile-time filter predicates swapped:

• compileIncoming skipped the default header read whenever a custom outgoing mapping existed, so MapOutgoingProperty(x => x.Foo, ...) silently deleted the incoming "foo" header read.
• compileOutgoing did the symmetric wrong thing — MapIncomingProperty(x => x.Foo, ...) silently deleted the outgoing "foo" header write.

The reporter observed it on Kafka:

mapper.MapIncomingProperty(x => x.Id, ...);
// outgoing messages no longer carry the "id" header at all

Each filter now correctly checks its own direction's dictionary, so MapIncomingProperty / MapOutgoingProperty truly affect only the direction their name implies.

Verification

• 4 new regression tests in MapIncomingPropertyTests cover both directions + sanity checks that the customization itself still wins on the direction it targets. They fail on main and pass with this change.
• Full CoreTests net9.0 run: 1350/1350 pass.
• Full Wolverine.Kafka.Tests net9.0 run: 142/142 pass (2 pre-existing flaky skips). Kafka exercises this codegen end-to-end on a live broker.

Test plan

• Reproducer tests fail on unfixed code
• Reproducer tests pass after the fix
• Full CoreTests pass (no regression in shared mapper codegen)
• Full Kafka tests pass (live transport exercising the mapper)

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