Ssz encoding generator

[flcl42]

Changes

• Adds ssz generator that supports all stuff except stable containers

Types of changes

What types of changes does your code introduce?

• Bugfix (a non-breaking change that fixes an issue)
• New feature (a non-breaking change that adds functionality)
• Breaking change (a change that causes existing functionality not to work as expected)
• Optimization
• Refactoring
• Documentation update
• Build-related changes
• Other: Description

Testing

Requires testing

• Yes
• No

If yes, did you write tests?

• Yes
• No

[LukaszRozmej]

ArrayPoolList?

[flcl42]

ArrayPoolList seems a bit too complex for such task. Mind we add something like

public struct ArrayPoolSpan<T>(ArrayPool<T> arrayPool, int length) : IDisposable
{
    private readonly T[] _array = arrayPool.Rent(length);
    private readonly int _length = length;

    public ArrayPoolSpan(int length) : this(ArrayPool<T>.Shared, length) { }

    public readonly ref T this[int index] => ref _array[index];

    public static implicit operator Span<T>(ArrayPoolSpan<T> self) => self._array.AsSpan(0, self._length);
    public static implicit operator ReadOnlySpan<T>(ArrayPoolSpan<T> self) => self._array.AsSpan(0, self._length);

    public readonly void Dispose() => arrayPool.Return(_array);
}

?

[emlautarom1]

LGTM. The source generator part looks quite tricky and I think very few people will want to work on it in case there are issues but I don't see any easy way to make them more "maintainable".

I'll most likely copy the Diagnostics code into the proposed RLP PR.