Issue #3466324 by mogtofu33, grimreaper: [1.0.0-alpha3] Config Schema: flatten structure

config/schema/ui_icons.schema.yml

...ons_ckeditor5/config/schema/ui_icons_ckeditor5.schema.yml

...i_icons_example/config/schema/ui_icons_example.schema.yml

...ons_bootstrap/config/schema/ui_icons_bootstrap.schema.yml

...ules/ui_icons_dsfr/config/schema/ui_icons_dsfr.schema.yml

...i_icons_feather/config/schema/ui_icons_feather.schema.yml

...fontawesome/config/schema/ui_icons_fontawesome.schema.yml

...ons_heroicons/config/schema/ui_icons_heroicons.schema.yml

...i_icons_icomoon/config/schema/ui_icons_icomoon.schema.yml

...icons_material/config/schema/ui_icons_material.schema.yml

...icons_octicons/config/schema/ui_icons_octicons.schema.yml

.../modules/ui_icons_octicons/ui_icons_octicons.ui_icons.yml

...icons_phosphor/config/schema/ui_icons_phosphor.schema.yml

...ons_remixicon/config/schema/ui_icons_remixicon.schema.yml

...es/ui_icons_uswds/config/schema/ui_icons_uswds.schema.yml

...es/ui_icons_field/config/schema/ui_icons_field.schema.yml

...s/config/schema/ui_icons_field_link_attributes.schema.yml

modules/ui_icons_field/ui_icons_field.module

modules/ui_icons_text/config/schema/ui_icons_text.schema.yml

...ules/ui_icons_test/config/schema/ui_icons_test.schema.yml