fix(test-focil): omit inclusion list result for invalid payloads

[chugarchugarr]

Description

Fixes #3436.

Engine API payload metadata only has a meaningful inclusionListSatisfied result when the payload itself is valid. The FOCIL filler previously carried the transition-tool result into engine_newPayload fixtures even when the same BuiltBlock was marked invalid.

BuiltBlock.get_fixture_engine_new_payload() now:

• preserves True and False for valid payloads;
• emits None for invalid payloads, as the Engine API requires.

The focused regression covers all four valid/invalid and satisfied/unsatisfied combinations.

Verification

• uv run pytest -q packages/testing/src/execution_testing/specs/tests/test_focil_payload_metadata.py — 4 passed
• Ruff check and format check — passed
• git diff --check — passed

Scope

• no change to inclusion-list evaluation
• no change to valid-payload metadata
• no production fork behavior change

Base

devnets/focil/0 at 23b0358c3513c8d22324faea66b41cec4b0b6446.