fix(new-arch): metro warning for Flyout/Popup

[frankcalise]

Description

Type of Change

• New feature (non-breaking change which adds functionality)

Why

While building an app in the New Architecture template, if you use either <Flyout /> or <Popup /> you'll be met with the unsupported Fabric view red box. This error is displayed from RN core.

Additionally, we can display a Metro warning to make the error more clear to the user - that they should be migrating to <Modal />

Resolves #14671

What

1. Detects if we're running Fabric via global.nativeFabricUIManager
2. Outputs a warning via console.warn in the contructors of Flyout and Popup

Screenshots

Collapsed Warning	Expanded Warning

Testing

Manually tested by editing node_modules\react-native-windows\Libraries\Components\Flyout\Flyout.js

Changelog

Should this change be included in the release notes: No

Microsoft Reviewers: Open in CodeFlow

[acoates-ms]

Please run yarn change to generate a change file for this change.
And I think we should probably use the warnOnce method to display the warning?

[frankcalise]

@acoates-ms sure thing, should it bump the prelease version if it is just a warning in this case?

[acoates-ms]

/azp run

[azure-pipelines]

Azure Pipelines successfully started running 2 pipeline(s).