Normally only post-merge blocks (with difficulty of 0) are allowed, but the genesis block is often configured with non-zero difficulty even for chains that are post-merge from genesis.

op-program: Fix l2 engine API to avoid fetching L2 blocks after the chain head as part of importing.

Moves the engine API implementation to be part of op-program production code

* op-node,contracts-bedrock: dynamic gas limit via SystemConfig

* specs: fix gas limit type

* specs: test missing gas limit

* op-chain-ops: fix system config initialize call, use default L2 gas limit

* go: update op-geth dependencies for dynamic gas limit change

* op-chain-ops: fix 2nd missing default

op-e2e: actiont test l2 block building - deposit processing needs to prepare state before applying tx