Update default config values to support 20 min epoch for staging

[Yashk767]

Description

Currently the develop branch has config values set to support 5 min epoch and the same values might not work for 20 min epoch, rather they should be set to support a larger 20 min epoch by default. If the default values are set to support 20 min epoch, they would also support 5 min shorter epoch if the config values are set correctly by the user.

Implementation

Update the default, maximum and minimum config values in core/constants.go and cmd/config-utils.go` should be updated to support 20 min epoch.