Review `rose-app.conf` files in recipe test workflow

[alistairsellar]

Is your feature request related to a problem? Please describe. Two aspects of rose-app.conf files in particular need review:

• Scripts in app/process/bin, app/compare/bin and app/install_env_file/bin only execute a single line of code (excluding variable setting and directory creation), which could be encoded in the rose-app.conf command instead.
• Exposure of environment variables to user. In most cases the variables in the env section should not be edited by users, and therefore should perhaps be specified in the suite-level environment, not app level.

Would you be able to help out? Yes

[ehogan]

If we decide to retain any of the Bash scripts, we should implement shellcheck in the GitHub workflow for the RTW 😊