Make MAUI trimming safe ✂️

[marek-safar]

As part of the .NET6 effort we are making the .NET Runtime trimming safe allow developers to annotate their libraries to be also trimming safe. As MAUI is one of the primary workloads which will always use linker and cares about the size it's important to resolve any linker warnings which the developers would experience when enabling linker analyzers in their apps to be able to trim their apps fully.

This will partially depend on the work done for Apple, Android and WinUI SDKs but it's not blocked by them.

[Redth]

There are a few things that will immediately help us progress here. We are moving to a more code/API based approach to registering things like handlers instead of scanning for assembly level attributes when assemblies are loaded. In areas where we still want (or need) to support these types of scenarios we can move towards using source code generators to generate the api invocations so that the linker can still be aware of usages and have them not linked out.

Agree overall, being trimming safe is a priority for MAUI.

[marek-safar]

Using source generators is certainly a step in the right direction. You can use the tooling to identify linker unsafe code today if you need to.

[Redth]

Closed - tracking in #1962