EVM: update transaction base cost

Context

The base cost of transactions has a more fine grained cost structure that previously implemented. Specifically, there is a cost associated with the size of transaction input data, and additional costs associated with contract create. This MR goes towards getting the price of contract creation right.

Corresponds to G_txdatazeo, G_txdatanonzero and G_create in Appendix G of Yellow paper.

Transaction data cost is

• 4 per 0 byte
• 16 per non zero byte

Contract creation cost is 32000 (plus the standard 21000).

Manually testing the MR

Price updates should be reflected in updates to unit tests. Run them as part of CI.

Checklist

• Document the interface of any function added or modified (see the coding guidelines)
• Document any change to the user interface, including configuration parameters (see node configuration)
• Provide automatic testing (see the testing guide).
• For new features and bug fixes, add an item in the appropriate changelog (docs/protocols/alpha.rst for the protocol and the environment, CHANGES.rst at the root of the repository for everything else).
• Select suitable reviewers using the Reviewers field below.
• Select as Assignee the next person who should take action on that MR