feat(icrc-ledger-types): add ICRC-123 block schema validators

[bogwar]

Phase 1 of ICRC-123/153 implementation. Adds ICRC-123 block schema validators for 4 block types with permissive and strict validation modes.

[gregorydemay]

Thanks @bogwar I mostly have some understanding questions but otherwise code LGTM

[gregorydemay]

nit: this seems to be almost the same as principal_block_validator. If you want to keep the expressivity (2 different method names) I would refactor so that they delegate to a common internal method.

[bogwar]

The two functions differ only in the required tx field (account with is_account() vs principal with is_principal()). I could extract a common helper that takes the field name and predicate as parameters, but it would add indirection for very little deduplication — the outer block structure (phash, btype, ts, tx) is the same but the tx field predicates are different. Happy to refactor if you feel strongly.

[bogwar]

On reflection, I'd rather keep them separate. The deduplication gain is minimal (one line differs) and a shared helper with field name + predicate parameters would be harder to read. Keeping them explicit makes it clear at a glance what each block type expects.

[gregorydemay]

understanding question: the ICRC number appears in certain methods, like validate_153_freeze_account but not all, like this one (validate_freeze_account). Is there a reason?

[bogwar]

Good point — renamed all permissive validators to include the standard number: validate_123_freeze_account, validate_123_unfreeze_account, etc. The convention is now: validate_123_* = permissive (ICRC-123 block standard), validate_153_* = strict (ICRC-153 endpoint standard). Created DEFI-2791 to apply the same rename to the ICRC-122 module (validate_mint → validate_122_mint).