Add fast-runtime feature for faster time constants for local testing

[dastansam]

This came up when testing upgrade_domain_runtime in a local network. In addition to RuntimeUpgradeDelay, we could set other timing constants to faster values as well

[NingLin-P]

Make sense, I usually update these constants manually before building the binary for the local test network.

An alternative is to move these constants to pallet-runtime-config and export extrinsic to update these values, though extract effort is required to ensure the update will take effect as expected.

[nazar-pc]

I usually just update the things I need and often store in chain spec so it doesn't change between recompilations when many restarts are needed. Not sure about the feature though.