Prefix secrets with DBT_ENV_SECRET_ for test env vars #2663

Job	Run time
code-quality	1m 40s
build packages	15s
unit test / python 3.8	1m 20s
unit test / python 3.9	1m 28s
unit test / python 3.10	1m 30s
unit test / python 3.11	1m 19s
verify packages / python 3.8 / ubuntu-latest	31s
verify packages / python 3.9 / ubuntu-latest	36s
verify packages / python 3.10 / ubuntu-latest	29s
verify packages / python 3.11 / ubuntu-latest	32s
verify packages / python 3.8 / macos-12	47s
verify packages / python 3.9 / macos-12	52s
verify packages / python 3.10 / macos-12	48s
verify packages / python 3.11 / macos-12	1m 38s
verify packages / python 3.8 / windows-latest	1m 31s
verify packages / python 3.9 / windows-latest	1m 35s
verify packages / python 3.10 / windows-latest	1m 16s
verify packages / python 3.11 / windows-latest	2m 4s
	20m 11s

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