Add slot support to Pajamas alert component

app/components/diffs/overflow_warning_component.html.haml

app/components/pajamas/alert_component.html.haml

app/components/pajamas/alert_component.rb

...s/admin/application_settings/service_usage_data.html.haml

...ws/admin/dashboard/_security_newsletter_callout.html.haml

app/views/admin/groups/_form.html.haml

app/views/admin/projects/show.html.haml

app/views/admin/runners/edit.html.haml

app/views/admin/users/_users.html.haml

app/views/clusters/clusters/_banner.html.haml

app/views/clusters/clusters/_deprecation_alert.html.haml

...iews/clusters/clusters/_gcp_signup_offer_banner.html.haml

...roups/_import_group_from_another_instance_panel.html.haml

app/views/groups/_import_group_from_file_panel.html.haml

app/views/groups/settings/_export.html.haml

app/views/groups/settings/_remove_button.html.haml

app/views/groups/settings/_transfer.html.haml

app/views/import/shared/_errors.html.haml

...ws/layouts/header/_registration_enabled_callout.html.haml

...iews/layouts/header/_storage_enforcement_banner.html.haml