Work item Epic inline color widget

...ls/labels_select_widget/dropdown_contents_create_view.vue

...s/javascripts/sidebar/components/sidebar_color_picker.vue

...ets/javascripts/sidebar/components/sidebar_color_view.vue

...ts/work_items/components/work_item_attributes_wrapper.vue

app/assets/javascripts/work_items/constants.js

...ascripts/work_items/components/work_item_color_inline.vue

...items/graphql/work_item_metadata_widgets.fragment.graphql

...pts/work_items/graphql/work_item_widgets.fragment.graphql

...ork_items/components/work_item_attributes_wrapper_spec.js

...tend/work_items/components/work_item_color_inline_spec.js

ee/spec/frontend/work_items/mock_data.js

spec/frontend/sidebar/components/sidebar_color_view_spec.js

spec/frontend/work_items/mock_data.js