Add support for LearnMore option

UsbContaminant dialog no longer uses AlertActivity/AlertController
as UI design has been updated to a custom design to support
the Learn more option.

The CL also incorporates string updates.

Bug: 132737150
Test: dumpsys usb add-port "matrix" ufp;
dumpsys usb set-contaminant-status "matrix" true
Change-Id: I2b27e60e48986e669ef9bfe0239a56430d14a5a2