Reject transactions for which there’s no chance for the chain to reach the required gas price

[rafal-ch]

This PR adds another check to the transaction acceptor.

It makes the acceptor reject transactions with gas price tolerance set to a value that is not achievable by the chain within the given TTL.

Calculation is based on the assumptions that chain gas price can only go up and down by 1 every each era.

Additionally, this PR also fixes the problem with the gas price being reset after the network upgrade. With the fix, the gas price is preserved across the upgrades, which is covered by a new NCTL upgrade test in the corresponding PR.

[rafal-ch]

bors try

[casperlabs-bors-ng[bot]]

try

Build succeeded:

• continuous-integration/drone/push

[rafal-ch]

bors try

[casperlabs-bors-ng[bot]]

try

Build succeeded:

• continuous-integration/drone/push

[devendran-m]

Moving it back to backlog

[EdHastingsCasperAssociation]

After some back and forth deliberation, we decided to not include this in 2.0 rel