Use empty intial defaultRegion to let people use their project region config

[HyperBrain]

This is a Feature Proposal

Description

The plugin should set the defaultRegion parameter to an empty string, so that it would not add any region parameter to the serverless command line. This will automatically use the user's configured project region (serverless.yml) in the first place. Otherwise it could lead to an unexpected deployment into the wrong region (thanks @panzupa).

Similar or dependent issue(s):

• Support globally installed serverless #1 (comment)

Additional Data

• Extension version:
• Serverless Framework:
  Version:

• Serverless installed globally

• Operating System:
• Stack Trace (if available):