Create a wrapper script to support format stress tests in Evergreen

Summary:
Create a wrapper script to support format stress tests in Evergreen.

The new wrapper script is to call the existing test/format program iteratively to simulate the stress jobs currently running continuously in Jenkins, with the ease of use in Evergreen. 

The script parameters could include:

• expected runtime of the script
• number of test/format runs in parallel
• test hung threshold (e.g. runtime of a single iteration)