Upgrade to AWS provider 3.0 and add EMR resource names to be configurable

[sarahkb125]

I would like to merge 2 major changes (and one minor one).

Major changes:

• Support AWS provider version 3. This just involved changing a couple variable formats (roles --> role) in the EMR module and suppressing warnings by removing quotations around types and variables.
• Allow users of these modules to input custom resource names for EMR nodes. For instance, the master instance name was hard coded to master_group. I've added a variable master_instance_name that is defaulted to master_group to be backwards compatible, but also allows the user to abide by any naming conventions already put in place.
• Lastly, fixed a typo: segmnet_emr_autoscaling_policy --> segment_emr_autoscaling_policy