Components package: deprecated lifecycle method warning in slot-fill

[vindl]

The components package is using the deprecated componentWillUpdate lifecycle method which produces console warnings when executed in React strict mode.

gutenberg/packages/components/src/slot-fill/fill.js

Lines 25 to 34 in 6928e41

	componentWillUpdate() {
	if ( ! this.occurrence ) {
	this.occurrence = ++occurrences;
	}
	const { getSlot = noop } = this.context;
	const slot = getSlot( this.props.name );
	if ( slot && ! slot.props.bubblesVirtually ) {
	slot.forceUpdate();
	}
	}

Warning: Unsafe lifecycle methods were found within a strict-mode tree:
    in Editor (created by _class)
    in _class (created by RemountOnPropChange(_class))
    in RemountOnPropChange(_class)
    ...

componentWillUpdate: Please update the following components to use componentDidUpdate instead: Fill

cc @youknowriad @gziolo

[youknowriad]

This one is probably not the easiest one to replace because I believe the "order" of which the fills get added is important. So I'm pinging @aduth he knows more about that.

[aduth]

Order is important, yes. I'll give it a look, and if there aren't tests already, will add them in the fix.

[aduth]

As I understand, this was fixed as of #15541.