Add 0.81 desktop test app

[JasonVMo]

Platforms Impacted

• iOS
• macOS
• win32 (Office)
• windows
• android

Description of changes

This adds the start of a desktop tester app for 0.81, located under apps/desktop.

• NOTE: This is a work in progress change where the app builds and bundles (but does not yet run successfully). I'm submitting as-is to help stage the work.

The changes fall into two categories: creation of the app itself and changes to codegenNativeComponent calls to get them to have codegen specs that actually build correctly. Note that most of the native component fixups have already been submitted previously.

Todo items:

• get the app successfully running
• integrate codegen into our build pipelines such that errors are caught before bundle time

[changeset-bot]

🦋 Changeset detected

Latest commit: 9b83fce

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 2 packages

Name	Type
@fluentui-react-native/menu-button	Patch
@fluentui/react-native	Patch

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[Saadnajmi]

why not fluent-tester-81 for parity? We can consolidate the apps when we remove 0.74 support afterwards