Install tool xxd to platform monitor container (sonic-net#19671)

#### Why I did it

After upgrading from bullseye to bookworm, pmon container no longer default installs tool xxd. The tool is used in mellanox simx platforms. The PR is to install xxd tool in the docker build file.

#### How I did it

Install xxd in platform monitor docker file.

#### How to verify it

Manual test

dockers/docker-platform-monitor/Dockerfile.j2

@@ -27,7 +27,8 @@ RUN apt-get update &&   \
         iputils-ping    \
         pciutils        \
         nvme-cli        \
-        ethtool
+        ethtool         \
+        xxd
 
 # smartmontools version should match the installed smartmontools in sonic_debian_extension build template
 RUN apt-get install -y -t bookworm-backports \