Combine flow deps add & flow deps install commands

[jribbink]

Problem

Currently, flow deps add and flow deps install are seperate commands. There is really no reason to separate these commands and it is advantageous to lean into the flow deps install functionality when adding dependencies to keep them up to date & reduce confusion.

Proposed solution

I propose that we combine these two commands into flow deps install, where the following behaviour applies (similar to the NPM model):

• No args: same behaviour as now
• Args: like flow deps add, but will also perform the flow deps install action

Dependencies

I have a feeling that this may introduce overhead for adding dependencies. If this is significant, we must consider more efficient dependency fetching mechanisms (i.e. batch retrieval of on-chain hashes or deployment block heights if possible) and only fetch full contract code for dependencies which have been updated.