Add logic to carma script to account for env var in carma-config (#2409)

* simple method

* add default image feature

* new way to handle default

* fix to use platform or messenger instead of hardcoding base

* integration tested

* default to platform .env not found

* fix local env

* better comments

* suppress unnecessary errors logs to be backwards compatible

* clarify comments

* notify using .env file

* reword to be specific

* reword again

* one last fix

* last fix

* add more comments