LE advertise data parsing refactor

* merge BTM_CheckAdvData and BTM_CheckEirData into GetFieldByType
* check wether AD data is properly formatted when the packet is
  received. Some controllers were returning malformed data that
  resulted in stack crashes for BT5 packets.
* add tests to verify the helpers work as expected

Test: added net_test_stack_ad_parser
Bug: 37671082
Change-Id: I49e43d7cf7d0a8ace1ee45d9b14b2b8440096b05