These changes make it significantly easier (and more organized) to manage environment variables, will help avoid conflicts with variables set/used elsewhere, and it also prevents `prebuild.sh` from hardcoding some of them - so that users can change certain environment variables without needing to re-run the entire `prebuild.sh` script
This also sets our mozconfig files to use these new environment variables directly
Signed-off-by: celenity <celenity@celenity.dev>
This should provide a superior experience and will help prevent ex. future issues if we change the values to be more complex
Signed-off-by: celenity <celenity@celenity.dev>