Setting NullabilityInfoContextSupport=false in NativeAOT doesn't remove NullableAttribute/NullableContextAttribute ctors

[eerhardt]

dotnet publish -c Release -r win-x64 -p:PublishAot=true -p:NullabilityInfoContextSupport=false -p:IlcGenerateMstatFile=true the following app:

<Project Sdk="Microsoft.NET.Sdk">

  <PropertyGroup>
    <OutputType>Exe</OutputType>
    <TargetFramework>net7.0</TargetFramework>
    <ImplicitUsings>enable</ImplicitUsings>
    <Nullable>enable</Nullable>
  </PropertyGroup>

  <ItemGroup>
    <PackageReference Include="Microsoft.Extensions.DependencyInjection" Version="7.0.0-*" />
  </ItemGroup>
</Project>

Console.WriteLine(new Microsoft.Extensions.DependencyInjection.ServiceCollection());

Inspect the .\obj\Release\net7.0\win-x64\native\HelloWorld.mstat using ildasm and open the Methods() method, which lists all the methods left in the app.

Expected results

The System.Runtime.CompilerServices.NullableAttribute::.ctor(uint8) and System.Runtime.CompilerServices.NullableContextAttribute::.ctor(uint8) methods should be trimmed from the app, so they should not be in the mstat file.

Actual results

These attributes are left in the app.

[MichalStrehovsky]

This is because of dotnet/runtimelab#1381.

We need to add support for assembly fullname="*". Can be done, just wasn't completely straightforward and I don't expect this to have meaningful savings. Custom attributes are a lot less costly in NativeAOT metadata format than in IL.