Update alloy.j2 to correctly embed env file variable options

Env file variable options such as `--stability.level public-preview` in your Ansible configuration cause them to be embedded without being escaped in double quotes in the env file. 

This causes upgrade failures whereby the `prerm` script for the alloy package attempts executing the unescaped half, causing dpkg to spit out the error `/var/lib/dpkg/info/alloy.prerm: 6: /etc/default/alloy: public-preview: not found` for a configuration like so
```
# Ansible Managed

CONFIG_FILE="/etc/alloy/config.alloy"
RESTART_ON_UPGRADE=true

CUSTOM_ARGS=--stability.level public-preview
```

Author: robigan

roles/alloy/templates/alloy.j2

@@ -6,5 +6,5 @@ CONFIG_FILE="/etc/alloy/config.alloy"
 RESTART_ON_UPGRADE=true
 
 {% for key, value in alloy_env_file_vars.items() %}
-{{ key}}={{value}}
+{{ key}}="{{value}}"
 {% endfor %}