Verifier string parse/encode incompatibility

[kralverde]

Currently, verifier strings are limited to 80 characters. Making a null tag vout for a verifier uses OP_PUSH (https://github.com/RavenProject/Ravencoin/blob/e48d932ec70267a62ec3541bdaf4fe022c149f0e/src/assets/assets.cpp#L4567). Reading the verifier hardcodes an allotment of 1 byte for length (https://github.com/RavenProject/Ravencoin/blob/e48d932ec70267a62ec3541bdaf4fe022c149f0e/src/assets/assets.cpp#L901). The last 1-byte OP_PUSH is 0x4b (75 dec) making this de-facto the longest verifier string as longer will error.