[Techsupport]Handle SAI kv pair if present in sai common profile (#3196)

### What I did
Handle the SAI key value pair if it is present in sai common profile rather than specific profile for mellanox platforms. The concept of common sai profile is introduced in sonic-net/sonic-buildimage#18074 . After this the techsupport started to fail because of the absence of SAI_DUMP_STORE_PATH

#### How I did it
Check if the variable is not present in platform specific file and then read the common file. If the common file is not accessible due to syncd being down, fallback to default path which is hardcoded.


#### How to verify it
Running techsupport and ensuring it exits with code 0

scripts/generate_dump

@@ -1266,8 +1266,19 @@ collect_mellanox_dfw_dumps() {
     trap 'handle_error $? $LINENO' ERR
     local platform=$(python3 -c "from sonic_py_common import device_info; print(device_info.get_platform())")
     local hwsku=$(python3 -c "from sonic_py_common import device_info; print(device_info.get_hwsku())")
+    local def_dump_path="/var/log/mellanox/sdk-dumps"
     local sdk_dump_path=`cat /usr/share/sonic/device/${platform}/${hwsku}/sai.profile|grep "SAI_DUMP_STORE_PATH"|cut -d = -f2`
 
+    if [ -z $sdk_dump_path ]; then
+        # If the SAI_DUMP_STORE_PATH is not found in device specific sai profile, check in common sai profile
+        sdk_dump_path=`docker exec syncd cat /etc/mlnx/sai-common.profile | grep "SAI_DUMP_STORE_PATH" |cut -d = -f2`
+        if [ -z $sdk_dump_path ]; then
+            # If the above two mechanisms fail e.g. when syncd is not running , fallback to default sdk dump path
+            sdk_dump_path=$def_dump_path
+        fi
+    fi
+
+
     if [[ ! -d $sdk_dump_path ]]; then
        # This would mean the SAI_DUMP_STORE_PATH is not mounted on the host and is only accessible though the container 
        # This is a bad design and not recommended But there is nothing which restricts against it and thus the special handling