init: Set sepolicy at runtime to allow bind mounts for configs and mo…

…dules

* Ensure the init.renderzenith.sh script has executable chmod permissions.
* Execute init.renderzenith.sh with 'magisk' seclabel.

This will fix kernel bind mount issues in Magisk 16.7+ when moving from
monolithic to split sepolicies.

Signed-off-by: joshuous <[email protected]>