feat: on_execution_payload fork choice test support

[brech1]

What type of PR is this?

Feature

What does this PR do? Why is it needed?

Add test harness support for the on_execution_payload fork choice step type and head_payload_status check for Gloas.

• Handle ExecutionPayloadEnvelope step in fork choice test runner
• Insert payload envelope for Gloas anchor blocks
• Gate on_execution_payload handler to Gloas and later forks
• Enable StartOptimistic for Gloas fork choice tests

To enable:

• Update consensus_spec_version to v1.7.0-alpha.3:

prysm/WORKSPACE

Line 276 in 36052ed

consensus_spec_version = "v1.7.0-alpha.2"

• Register test files after:

prysm/testing/spectest/mainnet/BUILD.bazel

Line 181 in 36052ed

"fulu__forkchoice__forkchoice_test.go",

prysm/testing/spectest/minimal/BUILD.bazel

Line 187 in 36052ed

"fulu__forkchoice__forkchoice_test.go",

Other notes for review

Let me know if this is useful, as it is right now it's just handlers code. I used this to check:

• Add initial fork choice tests for Gloas ethereum/consensus-specs#4940

Otherwise, I can close and leave the committed changes on my fork for future implementers.

Acknowledgements

• I have read CONTRIBUTING.md.
• I have included a uniquely named changelog fragment file.
• I have added a description with sufficient context for reviewers to understand this PR.
• I have tested that my changes work as expected.

[CLAassistant]

All committers have signed the CLA.