Implement demand-based base fee changes

The initial fee implementation has static base fees, for simplicity.

We should implement EIP-1559-style demand-based changes. Here we have to do some research on the concrete mathematical model to use. The mechanism in EIP-1559 may be a bit too sensitive and a better approach suggested to us was a momentum-based approach where the base fee increases in a larger step only if there are 3-4 blocks in a row that are above target utilization.

One option is also to start with the same model from EIP-1559 with some appropriate parameter changes (e.g. due to different block times in Miden vs Ethereum) and leave these advanced optimizations for later.

Broken out of https://github.com/0xMiden/miden-base/issues/1673.