feat(cancun): Cancun should be tested E2E from the relay POV

[david-bakin-sl]

With the Cancun upgrade (targeted: services 0.50) there should be end-to-end tests of (some of the) Cancun functionality from the relay POV.

Obviously Ethereum type 3 transactions (containing "blobs") need to be rejected as mentioned in #2390 .

But there could also be tests that Cancun functionality can be used: E.g., a contract using transient storage will work (instead of fail with invalid opcode).

See HIPs 865, 866, 867, and 868 for the scope of Cancun.

See related issue #725 in the smart contracts repo.