Allow null subscriberId in NetworkStatsManager.

Use a MATCH_MOBILE_WILDCARD template to avoid filtering by
subscriberId when querying statistics from NetworkStatsService.

Bug: 74038898
Change-Id: I8296220472a9ba37044dd1a5ede9bdb45d3ed339
Fixes: 74038898
Test: runtest frameworks-net, CTS tests pass
Merged-In: I1e4e283c6eaecf33d12488e41e0c524f6ff83954
Merged-In: Ia84d2c7cc63bf8b8bf30f133e0382fd7103bf490
(cherry-picked from aosp I4b39e7031416cb33b23d89aa36ff0f774eaa942f)