fix: adapt metadata MASM to little-endian word ordering after upstream migration

The upstream LE migration (PR #2512) changed get_item to return [word[0], ..., word[3]]
(word[0] on top) instead of [word[3], ..., word[0]]. This commit:

- Reverses element extraction logic in all getters (get_token_metadata, get_max_supply,
  get_decimals, get_token_symbol, get_token_supply, mutability checks)
- Fixes mutability flag extraction in all optional setters
- Fixes max_supply replacement logic in optional_set_max_supply
- Changes loc_storew_be/loc_loadw_be to loc_storew_le/loc_loadw_le to preserve
  natural word element ordering in memory for hash computations
- Updates test hasher from Rpo256 to Poseidon2 to match MASM poseidon2 module
- Fixes get_owner stack depth (get_item returns +2 net elements with 2-felt slot IDs)
- Updates all inline MASM test assertions to match LE stack ordering

Author: afa7789

crates/miden-standards/asm/standards/access/ownable.masm

@@ -89,6 +89,10 @@ end
 #! Invocation: call
 pub proc get_owner
     exec.owner
+    # => [owner_suffix, owner_prefix, pad(16)]  depth=18
+    # get_item returns 4 elements from 2 inputs (net +2); owner drops 2, leaving +2 excess.
+    # Remove 2 excess pad elements to restore call-convention depth of 16.
+    movup.2 drop movup.2 drop
     # => [owner_suffix, owner_prefix, pad(14)]
 end