Activate engine APIs even when genesis timestamp of hard fork is set to 0

[daniellehrner]

The following or similar genesis config are used on testnets or rollups:

{
  "config": {
    "chainId": 2151908,
    "homesteadBlock": 0,
    "eip150Block": 0,
    "eip155Block": 0,
    "eip158Block": 0,
    "byzantiumBlock": 0,
    "constantinopleBlock": 0,
    "petersburgBlock": 0,
    "istanbulBlock": 0,
    "muirGlacierBlock": 0,
    "berlinBlock": 0,
    "londonBlock": 0,
    "arrowGlacierBlock": 0,
    "grayGlacierBlock": 0,
    "mergeNetsplitBlock": 0,
    "shanghaiTime": 0,
    "cancunTime": 0,
    "bedrockBlock": 0,
    "regolithTime": 0,
    "canyonTime": 0,
    "ecotoneTime": 0,
    "fjordTime": 0,
    "graniteTime": 0,
    ...
}

Besu currently flattens those milestones, which leads to some engine API endpoints not being activated. See details in the following issue:

Consensys/op-besu#4

We need to make sure that those endpoints work as expected with those configurations