Add disallowed_platform_patterns

As part of EC-726, a new policy rule,
`buildah_build_task.platform_param`,  was added to prevent certain
platforms from being used based on the value of the
`disallowed_platform_patterns` rule data.

This commit disallows using platforms that include the `root` string.
This is the convention used to specify rootful hosts.

For the workflows that do require rootful access, use a policy config
that either disables the policy rule, or overrides the value of the rule
data to an empty list.

Ref: EC-726

Signed-off-by: Luiz Carvalho <[email protected]>

data/rule_data.yml

@@ -198,3 +198,6 @@ rule_data:
   - 2025-12-30
   - 2025-12-31
   - 2026-01-01
+
+  disallowed_platform_patterns:
+  - .*root.*