Allow anchor build/deploy to be given a keypair for the programid.

[akutruff]

Right now anchor build and anchor deploy generate a keypair in the target directory. This prevents being able to generate consistent program id's across different environments.

Suggest adding something like:
anchor build --program-keypair <keypair.json> and anchor deploy --program-keypair <keypair.json>
Which will use the provided keypair and not generate a file in the target directory.

[callensm]

This new argument would need to be only allowed if --program-name is specified, otherwise anchor build and anchor deploy act on all workspace programs.