Fix for - #3121 - vcfg command to set multiple configuration-store entries at a time

[schandrika]

Description

Added ability to add multiple agent configurations to configuration store using vcfg update-config-store command. This can be run when VOLTTRON is not running. One part of feature request #3121 This feature is very useful for automated deployment use cases where we auto generate multiple agent configurations before we deploy a VOLTTRON instance.

Fixes # (issue)

Type of change

Please delete options that are not relevant.

• [ ] Bug fix (non-breaking change which fixes an issue)
• [x] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to not work as expected)
• [ ] This change requires a documentation update

How Has This Been Tested?

Please describe the tests that you ran to verify your changes. Provide instructions so we can reproduce. Please also list any relevant details for your test configuration

• Manual testing with platform driver, economizer and ilc agent configurations and configuration metadata generated for intellimation
• Unit test cases in volttrontesting/platform/test_vcfg_config_update.py

Checklist:

• [x] My code follows the style guidelines of this project
• [x] I have performed a self-review of my own code
• [x] I have commented my code, particularly in hard-to-understand areas
• [x] I have made corresponding changes to the documentation
• [x] My changes generate no new warnings
• [x] I have added tests that prove my fix is effective or that my feature works
• [x] New and existing unit tests pass locally with my changes
• [ ] Any dependent changes have been merged and published in downstream modules