Add support for v1.6.0-alpha.4

[jtraglia]

PR Description

This PR adds support for the newest consensus-specs release:

• https://github.com/ethereum/consensus-specs/releases/tag/v1.6.0-alpha.4

There were some new SSZ tests. We can ignore the tests for progressive lists. The new Vector[boolean, N] tests are failing though, because we don't fully support this. I spent a little bit of time trying to figure it out, but I didn't love my solution so I think it would be best to let the team fix it. Here's some relevant code:

teku/eth-reference-tests/src/referenceTest/java/tech/pegasys/teku/reference/phase0/ssz_generic/SszGenericBasicVectorTestExecutor.java

Lines 77 to 82 in b15588c

	// vec_{element type}_{length}
	private SszSchema<?> getElementSchema(final TestDefinition testDefinition) {
	final String elementType = getElementType(testDefinition);
	return switch (elementType) {
	// bool is not a bit in this case, it's a full one byte boolean which we don't support
	case "bool", "uint8" -> SszPrimitiveSchemas.BYTE_SCHEMA;

Feel free to take over this PR & commit to the branch. Or tell me what to do and I'll make the changes.

Some of the failing tests:

An example of a failing test:

The relevant consensus-specs PRs:

• eip7916: add ProgressiveList specs and tests ethereum/consensus-specs#4445
• eip7916: add ProgressiveBitlist specs and tests ethereum/consensus-specs#4480

Also, no security concerns with this. The only instance of Vector[boolean, N] is in eip7732 here:

• https://github.com/ethereum/consensus-specs/blob/d00c9ae82e82d56086155f57d6377cc8d7d57f00/specs/_features/eip7732/fork-choice.md?plain=1#L131

Documentation

• I thought about documentation and added the doc-change-required label to this PR if updates are required.

Changelog

• I thought about adding a changelog entry, and added one if I deemed necessary.

[lucassaldanha]

Thanks for the PR @jtraglia! We'll try to look at it and add the missing bits :)

[jtraglia]

@lucassaldanha I've rebased this PR onto @zilm13's. Let's see if the reference tests pass. If they do pass, please merge Dmitrii's PR and mark this PR as ready for review.