* contracts-bedrock: remove GCT code

This commit removes the custom gas token code from the L2 contracts.
The interop contracts were tightly integrated into this code,
so the diff is quite large.

We cannot remove the getters from the `L1Block` contract because
chains did a genesis with `WETH` that calls out to the `L1Block`
contract. `WETH` is not proxied, so we cannot modify the bytecode
without an irregular state transition. Just going to leave the
functions on `L1Block` for simplicity.

Both the messenger and the bridge have the references to CGT removed.

* l1block: test coverage

* contracts-bedrock: more cleanup

* compiler error

* gas-snapshot

* contracts-bedrock: remove dead imports

* ctb: unused imports

* snapshots: update

* interfaces

* ctb: fix