Remove saving of Trial Environment variables and Constants in the measurement dataset

GCP-9959

Reviewer: Daniel Jao
Add unit tests for checking if environment variables and constants are being saved and retrieved correctly

GCP-9959

Reviewer: Daniel Jao
Move else statements after the right curly brace, use isEmpty to check if a collection has data, move trailing comments in a new line, put string literals at the start of the .equals comparison

GCP-9959

Reviewer: Daniel Jao