Enable sync with GitLab License database by default

In #398192 (closed) we disabled sync with GitLab License database by default. Now, as we have an application setting to control that, we can enabled it by default and disabled it for QA instances

Implementation plan

1. Disable sync for QA environment in .perform hook (it's called in the QA Template:

Runtime::ApplicationSettings.set_application_settings(package_metadata_purl_types: {})

2. Add migration to update package_metadata_purl_types_names column on application_settings page to Enums::PackageMetadata.purl_types_numerical.keys, it should be [1,2,3,...,12]. As well we need to add a condition to the migration to skip update if the current value is different from [] or [1,2,3,4,5,6,7,8,9,10,11,12]. That means that admins of self-hosted instance changed this setting to enable sync for the specific package registries and we should preserve this value.
3. Remove prerequisite from doc to enable the sync but add a mention in the License Scanning doc about enabling partial sync.