Why this should be merged

This PR implements ACP-176 with the exception of the allowance of empty blocks.

I will make a PR to update ACP-176 not to modify the validity condition of empty blocks with the reasoning that:

1. The usage of BlockGasCost has introduced some assumptions on the amount of gas consumed in a block.
2. While it is not unusual for the BlockGasCost to be 0, when it is non-zero the validator would still need to issue transactions with a sufficient fee to pay for the block gas cost.
3. In practice, there are not long periods of inactivity on either the fuji or mainnet C-chains.

How this works

This PR adds FUpgrade checks to the following critical behaviors:

1. The notion of GasCapacity is introduced. In verification and block building, GasCapacity replaces the prior usage of GasLimit. It is guaranteed for GasCapacity <= GasLimit.
2. GasUsed verification. This verification now merges the GasUsed and ExtraDataGasUsed and enforces the sum to be within the available GasCapacity.
3. The BaseFee, ExtraPrefix, and GasLimit functions were modified to include the ACP-176 definitions along with their corresponding verification functions.
4. The PredicateBytesFromExtra was expanded to account for the different extraPrefix sizes (depending on if the windower or acp-176 state is encoded)
5. The gas price bounds are modified to account for the lower allowed BaseFee.
6. The C-chain now allows users to configure their own GasTarget. When proposing blocks, the block proposer will move the chain's GasTarget toward their own GasTarget.

How this was tested

This PR includes unit tests for all of the modifications and additions to the header package.

Need to be documented?

Yes, the new GasTarget config should be documented.

Need to update RELEASES.md?

Yes the config changes should be included in the release notes.