Allow user to override initial configurables in forc-deploy

Similar to https://github.com/FuelLabs/sway/pull/5311, but for configurables.

>In my case I am starting to integrate upgradable contracts (proxies) and other things that do have different starting configurables. Our watchtower and l2 staking projects are very dependant on the bridge repository, and we won't be able to implement the e2e tests without developing a set of deploy scripts that could be very easily replaced by forc-deploy if it did not lack this feature.