Add limit to number of saved configs

Add an overlayable value config_wifiMaxNumWifiConfigurations to set the
max number of wifi configurations that can be saved on the device, and
then remove networks if a network is added past the max number.

Bug: 134726627
Test: atest FrameworksWifiTests
Change-Id: I245550636f73998784ce43106c0d0ce0b8eb7ee2
11 files changed