Invalid CI packaging setup, race condition in multitarget matrix

[Arlodotexe]

Background

See #250

Problem

Some components support only one of uwp or wasdk, plus a non-winui target like netstandard, such as uwp,netstandard or wasdk,netstandard. This creates a race condition:

1. Building wasdk first can produce a package with netstandard but without uwp.
2. Building uwp first can produce a package with netstandard but without wasdk.

Solution

This could be patched by deciding to build either UWP or WinUI first instead of doing it simultaneously, but there's a few reasons we don't. To understand why, consider:

• A component supporting uwp,netstandard could be fixed by not allowing wasdk to build first.
• A component supporting wasdk,netstandard could be fixed by not allowing uwp to build first.

Both cannot be done, meaning we must fix the issues with concurrent builds directly.

When building WinUI 2 or 3, we need to skip unsupported components.

• Skip building any component that have no WinUI-compatible targets (e.g. only netstandard).
• Skip building uwp,netstandard components if packaging for wasdk.
• Don't skip building wasdk,netstandard components if packaging for wasdk.
• Skip building wasdk,netstandard components if packaging for uwp.
• Don't skip building uwp,netstandard components if packaging for uwp.