Convert non-secrets to GitHub environment variables to improve troubleshooting

[ericmeans3cloud]

A number of the values passed to the GitHub workflows as secrets are not actually secrets and should be converted to variables. e.g. TRE_ID is not a secret value and could be a variable.

Converting these to variables would make it easier to verify that all values are present and correct if the deployment fails - this is mostly necessary when deploying a new TRE (especially when using manual auth as it's easy to forget to add a client ID or put the wrong one in).

The only ones that look like they actually should be secrets are:

API_CLIENT_SECRET
APPLICATION_ADMIN_CLIENT_SECRET
TEST_WORKSPACE_APP_SECRET
TEST_ACCOUNT_CLIENT_SECRET
AZURE_CREDENTIALS

[ericmeans3cloud]

Probably should have created this in the main repo, please transfer. :)