[EuiIcon] Fix setState errors when in React.StrictMode (#5899)

* fix(icon): early setState warning from Strict Mode

* docs: update changelog with #4874

* use this.state.icon in didMount

* Changelog

Co-authored-by: Phil Tietjen <tietjen.philip@gmail.com>

src/components/icon/icon.tsx

@@ -588,23 +588,31 @@ export class EuiIcon extends PureComponent<EuiIconProps, State> {
 
     const { type } = props;
     const initialIcon = getInitialIcon(type);
-    let isLoading = false;
-
-    if (isEuiIconType(type) && initialIcon == null) {
-      isLoading = true;
-      this.loadIconComponent(type);
-    } else {
-      this.onIconLoad();
-    }
 
     this.state = {
       icon: initialIcon,
       iconTitle: undefined,
-      isLoading,
-      neededLoading: isLoading,
+      isLoading: false,
+      neededLoading: false,
     };
   }
 
+  componentDidMount() {
+    const { type } = this.props;
+
+    if (isEuiIconType(type) && this.state.icon == null) {
+      //eslint-disable-next-line react/no-did-mount-set-state
+      this.setState({
+        neededLoading: true,
+        isLoading: true,
+      });
+
+      this.loadIconComponent(type);
+    } else {
+      this.onIconLoad();
+    }
+  }
+
   componentDidUpdate(prevProps: EuiIconProps) {
     const { type } = this.props;
     if (type !== prevProps.type) {

upcoming_changelogs/5899.md

@@ -0,0 +1,3 @@
+**Bug fixes**
+
+- Fixed `EuiIcon` from producing console warning in `React.StrictMode`