Fix OOB writes in gatt_sr.cc

At various points in gatt_sr.cc, the output of the
gatt_tcb_get_payload_size function is used without checking for a
positive length.  However, in exceptional cases it is possible for the
channel to be closed at the time the function is called, which will lead
to a zero length and cause an OOB write in subsequent processing.

Fix all of these.

Bug: 364026473
Bug: 364027038
Bug: 364027949
Bug: 364025411
Test: m libbluetooth
Test: researcher POC
Flag: EXEMPT trivial validity checks
Tag: #security
Ignore-AOSP-First: Security
(cherry picked from commit 7de5617f)
(cherry picked from https://googleplex-android-review.googlesource.com/q/commit:130861eadc3d9eda593df949666e561dd1f020fc)
Merged-In: I9b30499d4aed6ab42f3cdb2c0de7df2c1a827404
Change-Id: I9b30499d4aed6ab42f3cdb2c0de7df2c1a827404