Connected Execution: Set AWS_PROFILE for use by VSCode terminal, source control, etc.

When using VSCODE Source control to push code changes, it always goes to system associated with Default user profile, even thought AWS Toolkit has been changed to use a custom profile i.e C1

Steps to reproduce the behavior:
1. change from command pallete > AWS: Connect to AWS to use C1 profile, which has working keys in credentials file
2. from VSCODE Source control commit changes and push and it always goes to system associated with default profile not the currently set C1 profile

- OS: Win10
- Visual Studio Code Version: v1.50
- AWS Toolkit Version: 1.15.0 2020-10-06

Start by examining how the AWS: Connect to AWS command propagates the selected C1 profile to the VS Code terminal and source control environment. Reproduce on Windows with the listed VS Code and AWS Toolkit versions, then verify that commits and pushes use C1 rather than the default profile.

Written by the indexing model from the issue text.