Read AWS Credentials from aws-sdk

Is your feature request related to a problem? Please describe.
This stems from #1206, in where there might be a solution in where we can bake that feature requested into insomnia.

Describe the solution you'd like
So if the user doesn't define the access key, secret and/or session token we could just fallback to grabbing the credentials form the aws sdk.

So from the current code now:

We could just do add the following:



This would load whatever default credentials that the user has defined. It would also pick up a more complex setup like if they are using profiles or not.

Describe alternatives you've considered

Additional context