Output a status string when downloading the barretenberg CRS

[zac-williamson]

When using the Aztec sandbox, running yarn aztec-cli compile for the first time is very slow, because barretenberg is downloading its CRS.

Giving the user feedback that this is happening would be helpful, to prevent the user thinking that either:

a. something is wrong
b. compilation is very slow in the general case

This would require barretenbergs setup scripts to output status information, and then have aztec-cli forward this output to the console.