Prefix secrets with DBT_ENV_SECRET_ for test env vars (#995) #8256

Job	Run time
build packages	15s
code-quality	1m 15s
unit test / python 3.8	1m 51s
unit test / python 3.9	1m 41s
unit test / python 3.10	1m 17s
unit test / python 3.11	1m 0s
verify packages / python 3.8 / ubuntu-latest	36s
verify packages / python 3.9 / ubuntu-latest	49s
verify packages / python 3.10 / ubuntu-latest	40s
verify packages / python 3.11 / ubuntu-latest	44s
verify packages / python 3.8 / macos-12	56s
verify packages / python 3.9 / macos-12	1m 9s
verify packages / python 3.10 / macos-12	1m 36s
verify packages / python 3.11 / macos-12	1m 12s
verify packages / python 3.8 / windows-latest	2m 18s
verify packages / python 3.9 / windows-latest	2m 12s
verify packages / python 3.10 / windows-latest	2m 16s
verify packages / python 3.11 / windows-latest	2m 26s
	24m 13s

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