Default 5secs fake chain wastes people time

[DavidBruant]

I see at least two cases of using agoric-cli:

1. iterate (and do a modify->deploy->test-> loop) on a new smart contract
2. test how it may feel in real life

For the first case (likely the most frequent), the fake blockchain delay feels like it only gets in the way of working
I see value for the second case, but more as an opt-in, when the first phase is over

Currently, the default value is 5secs:

agoric-sdk/packages/agoric-cli/lib/start.js

Lines 5 to 7 in 0744788

	const FAKE_CHAIN_DELAY =
	process.env.FAKE_CHAIN_DELAY === undefined
	? 5

Could it be made at least configurable? edit: my mistake, it's already configurable via an environment variable. Could it be made configurable via a command-line argument?

And as a second step reduced to 0 or something below 1sec?