Enable reserved variable name checks and fix violations (#12463)

* Enable reserved variable name checks and fix violations

Updated .ansible-lint configuration to skip only var-naming[pattern]
and var-naming[no-role-prefix] instead of skipping the entire var-naming rule.
This enables the check for reserved variable names.

Renamed variables that used reserved names to avoid conflicts.
Updated all references in tasks, variables, and templates.

Signed-off-by: Ali Afsharzadeh <afsharzadeh8@gmail.com>

* Rename namespace variable inside tasks instead of deleting it

Signed-off-by: Ali Afsharzadeh <afsharzadeh8@gmail.com>

* Change hosts variable to vm_hosts

Signed-off-by: Ali Afsharzadeh <afsharzadeh8@gmail.com>

* Use k8s_namespace instead of dashboard_namespace in dashboard.yml.j2 template

Signed-off-by: Ali Afsharzadeh <afsharzadeh8@gmail.com>

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Signed-off-by: Ali Afsharzadeh <afsharzadeh8@gmail.com>