Add 1.23.1 release documentation

[keirthana]

• Add 1.23.1 release documentation
• Align with new release notes template model

Pending tasks:

• Add component versions once candidate is created
• Image versions need to be added
• Confirm known issue mentioned in comments with @adglkh
• Update bundle versions after promoting to stable

[adglkh]

Thanks for this

[adglkh]

@keirthana I'll make another comment and leave a workaround later on for the issue that we discussed over mm after BAT and GAT

[adglkh]

@keirthana I'll make another comment and leave a workaround later on for the issue that we discussed over mm after BAT and GAT

The following is something we'd like to add into the 1.23.1 release note. Please take a look.
Thanks

Since version 1.23.0, the Anbox WebRTC Data Proxy service starts on demand rather than at container startup. However, its startup time may take longer than expected, which can negatively impact the [out-of-band data exchange](https://documentation.ubuntu.com/anbox-cloud/en/latest/howto/stream/exchange-oob-data/#version-2) between the WebRTC server and client. This issue can be worked around by applying the following tweak in a [pre-start](https://anbox-cloud.io/docs/ref/hooks)
``
#!/bin/sh -ex
if  [ "$CONTAINER_TYPE" = "regular" ]; then
  exit 0
fi

DROP_IN_DIR=/etc/systemd/system/anbox-webrtc-data-proxy.service.d/
sudo mkdir -p "${DROP_IN_DIR}"
sudo tee "${DROP_IN_DIR}/override.conf" > /dev/null <<EOF
[Install]
WantedBy=multi-user.target
EOF

sudo systemctl daemon-reload
sudo systemctl enable anbox-webrtc-data-proxy
``

[adglkh]

@keirthana
As discussed in the SU, there is another item we'd like to add to the known issues.

For the Anbox Cloud appliance deployment, after it's initialized, you may encounter the following error when creating an application or launching an instance:
```
Failed to load kernel module ''anbox_sync'': Failed to run: modprobe -b anbox_sync: exit status 1 (modprobe: FATAL: Module anbox_sync not found in directory /lib/modules/x.x.x-xxxx-aws)'
```
To resolve this issue, please install the required package

    sudo apt install linux-headers-$(uname -r)

then reinstall anbox-modules-dkms-123 package

    sudo apt install --reinstall anbox-modules-dkms-123

After completing these steps, you should be able to create an application or launch an instance normally. The issue will be fixed in the next patch release.

[adglkh]

LGTM

[ajanon]

LGTM, thanks!