Add TestSmokeRPCCompatibilities for RPC compatibility smoke test

[Kourin1996]

Addresses https://github.com/celo-org/celo-blockchain-planning/issues/522

This PR adds smoke test for RPC compatibilities (Block, Transaction, Block Receipt, and Transaction Receipt).

Test retrieves these kinds of data at height 0, the last height of the L1 chain, and heights iterated every 1M blocks.

How to test

Make sure you have WebSocket RPC URLs of L1 and L2 full node.
Please note that TxLookUp must be enabled for all transactions in the nodes.

go test -v ./compat_test -tags compat_test -run TestSmokeRPCCompatibilities -celo-url ws://localhost:8546 -op-geth-url ws://localhost:9994

Optionally --block-interval and --random-block can be given:

# Test data at random heights every 10,000 block
go test -v ./compat_test -tags compat_test -run TestSmokeRPCCompatibilities -celo-url ws://localhost:8546 -op-geth-url ws://localhost:9994 --block-interval 10000 --random-block true

• block-interval: Number of blocks to skip between each test iteration. For instance, if set to 1,000,000, the test will be executed every 1 million blocks.
• random-block: Enables a random block height within a specified range to be selected for each test iteration

[piersy]

One suggestion, apart from that it's looking good!