Custom MMR IDs

[fmkra]

Added support for creating MMRs with custom IDs provided as an argument to functions create_branch_*.

NOTICE: Calling create_branch_from with mmr_id = 0, creates brand new mmr with size 1 and element equal to hash of brave new world string. Because of that mmr_id = 0 is reserved and can be only used in create_branch_from function; in other functions it panics.

NOTICE 2: Since absence of MMR in map is indicated by root having value 0, it would be impossible to distinguish no MMR and MMR with root 0 which could allow malicious user to overwrite existing MMR. Therefore, root = 0 is not allowed anywhere.

Moved contracts from l1 folder to herodotus-evm repository.

• l1/src/L1MessagesSender.sol -> src/core/x-rollup-messaging/outbox/AbstractStarknetMessagesSender.sol and src/core/x-rollup-messaging/outbox/L1ToStarknetMessagesSender.sol. It was split into two files for better abstraction
• l1/src/interfaces/* -> src/core/interfaces or src/core/x-rollup-messaging/interfaces