Move env var config loading to be within the config package. am: 2f504db7...

Move env var config loading to be within the config package. am: 2f504db7 am: 4d5f00fe am: 14325e74

Original change: https://googleplex-android-review.googlesource.com/c/platform/build/soong/+/18971604



Change-Id: I871dfacc58388b6af9e4a37380305c5009264e8c
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>