Enforce max recursion depth in VaultCreate, improve VaultDeposit checks

Also fix off-by-one error in recursive checks isFrozen and requireAuth

include/xrpl/protocol/Protocol.h

@@ -122,6 +122,8 @@ std::size_t constexpr maxDataPayloadLength = 256;
 /** Vault withdrawal policies */
 std::uint8_t constexpr vaultStrategyFirstComeFirstServe = 1;
 
+/** Maximum recursion depth for vault shares being put as an asset inside
+ * another vault; counted from 0 */
 std::uint8_t constexpr maxFreezeCheckDepth = 5;
 
 /** A ledger index. */