Ability to specify env in bos.config.json

[elliotBraem]

A couple of ecosystem projects set up their Github workflows to deploy to testnet, then to mainnet.
For example, see near-discovery-components (although this uses bos-loader exclusively).

To do this, there are different replacements file for each environment that get passed to bos-loader replacements flag.

See:

We should be able to support the same in bos-workspace.

Acceptance Criteria

• Builders should be able to assign different account Ids according to environment, e.g "mob.near" in mainnet and "eugenethedream" in testnet
• Builders should be able to assign different contract ids according to environment, e.g "devgovgigs.near" in mainnet and "thomas.preview.testnet" in testnet
• Builders should be able to assign other aliases according to environment(?)

[elliotBraem]

I also noticed today that bw deploy is strictly mainnet