Fix an OOB access bug in btm_vendor_specific_evt

This CL also fix one of vendor specific event callbacks:
BleAdvertiserVscHciInterfaceImpl::VendorSpecificEventCback.

Other issues in the callbacks of this function are:
- b/261857395, fix in I1ba4d1f1e62b1d77ac635cfb6b16cf175bfbf254.
- b/264921486, fix in Ifed6a81c2a980394efbd5666305d10227d5ec186,

Bug: 255304665
Test: manual
Ignore-AOSP-First: security
Tag: #security
Change-Id: Ic9c43064db88a36aecb2a88f024db85f6cfc05f1