Make MAX_REQUEST_BLOCKS runtime-configurable

[michaelsproul]

Description

In Deneb, the MAX_REQUEST_BLOCKS became configurable. We are currently using type-level numbers and constants for this on both stable and Deneb:

lighthouse/beacon_node/lighthouse_network/src/rpc/methods.rs

Lines 24 to 26 in 203ac65

	/// Maximum number of blocks in a single request.
	pub type MaxRequestBlocks = U1024;
	pub const MAX_REQUEST_BLOCKS: u64 = 1024;

lighthouse/beacon_node/lighthouse_network/src/rpc/methods.rs

Lines 32 to 33 in 203ac65

	pub type MaxRequestBlocksDeneb = U128;
	pub const MAX_REQUEST_BLOCKS_DENEB: u64 = 128;

Ideally we would like to be able to configure this on a per-network basis, which would mean getting rid of the compile-time constants. This might be quite hard to do.

Steps to resolve

Easier option

• Add max_request_blocks and max_request_blocks_deneb to the chain spec and ensure that the runtime-configured values match the compile-time ones (fail with an invalid config error if not).

Harder option

• Refactor blocks by root requests to not use compile-time constants.
• Remove all uses of constants related to MAX_REQUEST_BLOCKS. E.g. this one.

[michaelsproul]

Previous versions of Teku were being pernickety about Lighthouse not including this value on the /eth/v1/config/spec endpoint, but IMO that's their problem (and they've fixed it now).

Keeping this issue and closing #4711.

[michaelsproul]

Accidental duplicate of #4562