wifi: Params for SAR limits

Add 2 new config.xml values for setting TX power limits for SAR
requirements. The first boolean enables/disables the whole feature, the
second value sets the max power that OEM's can set if they want the tx power
to be limited.
Also, added the new HAL feature set enum value in WifiManager.

Bug: 62437848
Test: Compiles
Change-Id: Iab3ffad8df2fccd0ea2beac95fbf8458e268f21b