SingleWriterBpfMap - introduce getSingleton with caching am: 52d6c5587f am: 3f61e89bcf

Original change: https://android-review.googlesource.com/c/platform/packages/modules/Connectivity/+/3134198

Change-Id: Ic31627af2dc6bc01691fd184bf94385dc55bc8c3
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>