op-fetcher improvements

I would like to make op-fetcher a service that I use in my daily flow, but there are a few changes to reduce friction which I'd like to see.

1. Should only require one input address: currently both the SystemConfig and L1StandardBridge addresses are needed as input, but one or the other should be sufficient depending on the version of the systemconfig.
2. Should be able to get the rpc url from the $ETH_RPC_URL env var.
3. Should print to std-out if not provided an out-file arg.

Basically I want to be able to call it with no more than:

```
$ op-fetcher --system-config 0x229047fed2591dbec1eF1118d64F7aF3dB9EB290
```

Compare to this [bash script](https://gist.github.com/maurelian/a9b7b2ccb0cca1806bdf05442038a9b1) I use on my machine, that's basically the UX I'm going for:

```
$ readSystemConfig 0x229047fed2591dbec1eF1118d64F7aF3dB9EB290
Reading SystemConfig addresses from 0x229047fed2591dbec1eF1118d64F7aF3dB9EB290...
----------------------------------------
L1CrossDomainMessenger: 0x25ace71c97B33Cc4729CF772ae268934F7ab5fA1
L1ERC721Bridge: 0x5a7749f83b81B301cAb5f48EB8516B986DAef23D
L1StandardBridge: 0x99C9fc46f92E8a1c0deC1b1747d010903E884bE1
DisputeGameFactory: 0xe5965Ab5962eDc7477C8520243A95517CD252fA9
OptimismPortal: 0xbEb5Fc579115071764c7423A4f12eDde41f106Ed
OptimismMintableERC20Factory: 0x75505a97BD334E7BD3C476893285569C4136Fa0F
PermissionedGame: 0x1Ae178eBFEECd51709432EA5f37845Da0414EdFe
FaultGame: 0x5738a876359b48A65d35482C93B43e2c1147B32B
AnchorStateRegistry: 0x1c68ECfbf9C8B1E6C0677965b3B9Ecf9A104305b
DelayedWETHPermissioned: 0x21429aF66058BC3e4aE4a8f2EC4531AaC433ecbC
DelayedWETHPermissionless: 0x323dFC63c9B83CB83f40325AaB74b245937cbdF0
VM: 0xF027F4A985560fb13324e943edf55ad6F1d15Dc1
PreimageOracle: 0x1fb8cdFc6831fc866Ed9C51aF8817Da5c287aDD3
```