Remove both help and search icons from toolbar of wifi calling

On Android S, both help and search icons will be removed from each
toolbar of subsetting page. Using a feature flage to turn on/off these
menu items. After the collaping toolbar feature rolled out, the option
menu of toolbar will be removed entirely.

Bug: 177640645
Test: visual verified
Change-Id: I005fe85f23f8d28b3a6ca273ddb86ad3390ee0da