android/gatt: Use g_attrib buffer where possible for att
android/gatt: Use g_attrib buffer where possible for att

This replaces fixed size pdu usage with g_attrib buffer when possible.
When only received packets are decoded we use dynamic allocation with
current mtu.

silent-snowman/bluez,mapfau/bluez,pkarasev3/bluez,pkarasev3/bluez,pkarasev3/bluez,pstglia/external-bluetooth-bluez,pstglia/external-bluetooth-bluez,ComputeCycles/bluez,silent-snowman/bluez,silent-snowman/bluez,pstglia/external-bluetooth-bluez,ComputeCycles/bluez,mapfau/bluez,pkarasev3/bluez,silent-snowman/bluez,pstglia/external-bluetooth-bluez,ComputeCycles/bluez,mapfau/bluez,mapfau/bluez,ComputeCycles/bluez