GAS: Add a generic GAS query module

GAS: Add a generic GAS query module

This implements GAS request mechanism that is aimed at being used to
replace use case specific GAS/ANQP implementations in the future.
Compared to the earlier implementation in P2P SD, this implementation
includes support for multiple concurrent requests and more thorough
validation of frames against the pending query data.

GAS header processing, including comeback and reassembly, are handled
within gas_query.c and the users of this module will only need to
provide the Query Request and process the (possibly reassembled)
Query Response.