Gas price increase on resubmission attempts for relayer

[rach-id]

After #636 is merged, we will have the transaction speed up functionality implemented. Then, we can add the following configurable parameters:

• boost factor: which the percentage by which the gas price is increased to ensure faster inclusion of the transaction in periods of congestion
• number of retries: which is the number of times the boost factor will be applied

This would give us greater control of the relayer transaction submission mechanism and be able to tune it depending on the level of congestion of the network.