Handle bad packet length in gatts_process_read_req

Added error check and handling code in gatts_process_read_req to
make sure that the packet length is correct.
Please note that there is another earlier CL that is reverted and this
is the updated one.

Bug: 73172115
Test: Run the test program, poc, that was attached in the bug report
Change-Id: Ia9b4e502fa8f8384bf9767e68f73b48a0915141b