Previously, the "avoid bad WiFi" global setting was limited to a single boolean value (0 or 1),
preventing granular control for multiple carriers.
This commit introduces support for carrier-aware "avoid bad WiFi" configurations using a new,
extensible format: "subId1,value1;subId2,value2;...".
This allows different `subId`s (carriers) to have their own specific "avoid bad WiFi" settings.
Flag: EXEMPT mainline
Bug: 410976315
Test: atest ConnectivityCoverageTests:android.net.connectivity.com.android.server.connectivity.MultinetworkPolicyTrackerTest
Change-Id: I118cff67c0c632778f73649999ee63e6f0e6fb17
cbdfd9f54b