Feature request: switch aws cli profile from within pacu

[sfellows-tii]

Currently, when invoking aws cli commands (e.g. 'aws configure list'), the aws cli profile is the same as when pacu was started. If you want to switch to another aws cli profile, you have to quit pacu, change the aws cli profile, then restart pacu. It would be nice to be able to do this from within pacu or be able to invoke a shell to do this.

I am using the swap_keys functionality in pacu to run modules, etc. using different credentials. It is only when invoking aws commands that there is a mismatch between profiles.