shared/gatt-client: Simplify read long value
shared/gatt-client: Simplify read long value

This removes the extra queue that acts as intermediate storage, instead
the code will now storage everything in a single buffer and just realloc
while appending new chunks.

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