Move py-cachetools to src folder am: c9b01f8f0f

Original change: https://android-review.googlesource.com/c/platform/external/python/cachetools/+/2219104

Change-Id: Icf306eb2a9e180db73105bef6f26b92e78465a39
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>