Fix first round of trim warnings

[eerhardt]

• DefaultOptionsProvider.TryGetAzureRoleInstanceIdNoThrow use Type.GetType to check for Microsoft.WindowsAzure.ServiceRuntime.RoleEnvironment, so the trimmer knows to preserve this type, if it is in the app
• ChannelMessage use the added public API for ChannelReader CanCount and Count, but fallback to reflection on netcoreapp3.1, since those APIs are not available on that runtime.

Contributes to #2449

This at least removes the warnings from using Microsoft.Extensions.Caching.StackExchangeRedis.

We could also add a trimming test app as outlined in https://learn.microsoft.com/en-us/dotnet/core/deploying/trimming/prepare-libraries-for-trimming#show-all-warnings-with-sample-application, along with a unit test that publishes the app and ensures there are no new warnings. LMK if you think this is valuable.

There are still these warnings left in this library:

/_/src/StackExchange.Redis/ScriptParameterMapper.cs(173): Trim analysis warning IL2070: StackExchange.Redis.ScriptParameterMapper.IsValidParameterHash(Type,LuaScript,String&,String&): 'this' argument does not satisfy 'DynamicallyAccessedMemberTypes.PublicConstructors', 'DynamicallyAccessedMemberTypes.PublicMethods', 'DynamicallyAccessedMemberTypes.PublicFields', 'DynamicallyAccessedMemberTypes.PublicNestedTypes', 'DynamicallyAccessedMemberTypes.PublicProperties', 'DynamicallyAccessedMemberTypes.PublicEvents' in call to 'System.Type.GetMember(String)'. The parameter 't' of method 'StackExchange.Redis.ScriptParameterMapper.IsValidParameterHash(Type,LuaScript,String&,String&)' does not have matching annotations. The source value must declare at least the same requirements as those declared on the target location it is assigned to. [C:\git\azure-activedirectory-identitymodel-extensions-for-dotnet\test\Microsoft.IdentityModel.AotCompatibility.TestApp\Microsoft.IdentityModel.AotCompatibility.TestApp.csproj]
/_/src/StackExchange.Redis/ScriptParameterMapper.cs(227): Trim analysis warning IL2070: StackExchange.Redis.ScriptParameterMapper.GetParameterExtractor(Type,LuaScript): 'this' argument does not satisfy 'DynamicallyAccessedMemberTypes.PublicConstructors', 'DynamicallyAccessedMemberTypes.PublicMethods', 'DynamicallyAccessedMemberTypes.PublicFields', 'DynamicallyAccessedMemberTypes.PublicNestedTypes', 'DynamicallyAccessedMemberTypes.PublicProperties', 'DynamicallyAccessedMemberTypes.PublicEvents' in call to 'System.Type.GetMember(String)'. The parameter 't' of method 'StackExchange.Redis.ScriptParameterMapper.GetParameterExtractor(Type,LuaScript)' does not have matching annotations. The source value must declare at least the same requirements as those declared on the target location it is assigned to. [C:\git\azure-activedirectory-identitymodel-extensions-for-dotnet\test\Microsoft.IdentityModel.AotCompatibility.TestApp\Microsoft.IdentityModel.AotCompatibility.TestApp.csproj]
/_/src/StackExchange.Redis/ScriptParameterMapper.cs(260): Trim analysis warning IL2026: StackExchange.Redis.ScriptParameterMapper.GetParameterExtractor(Type,LuaScript): Using member 'System.Linq.Expressions.Expression.Property(Expression,String)' which has 'RequiresUnreferencedCodeAttribute' can break functionality when trimming application code. Creating Expressions requires unreferenced code because the members being referenced by the Expression may be trimmed. [C:\git\azure-activedirectory-identitymodel-extensions-for-dotnet\test\Microsoft.IdentityModel.AotCompatibility.TestApp\Microsoft.IdentityModel.AotCompatibility.TestApp.csproj]
/_/src/StackExchange.Redis/ScriptParameterMapper.cs(261): Trim analysis warning IL2026: StackExchange.Redis.ScriptParameterMapper.GetParameterExtractor(Type,LuaScript): Using member 'System.Linq.Expressions.Expression.Call(Expression,String,Type[],Expression[])' which has 'RequiresUnreferencedCodeAttribute' can break functionality when trimming application code. Creating Expressions requires unreferenced code because the members being referenced by the Expression may be trimmed. [C:\git\azure-activedirectory-identitymodel-extensions-for-dotnet\test\Microsoft.IdentityModel.AotCompatibility.TestApp\Microsoft.IdentityModel.AotCompatibility.TestApp.csproj]

Fixing those will require a bit more work, as the whole LuaScript functionality looks like it needs to be marked RequiresUnreferencedCode.

cc @mgravell @NickCraver

[NickCraver]

Awesome! Not for this PR, but I'd be curious what a trim example looks like, and what it adds to test runtime overall. I'd like to ensure no breaks but when I last tried this the time cost was pretty high - can we do the check itself fairly quickly these days?

[eerhardt]

can we do the check itself fairly quickly these days?

There are 2 routes we can take to enable checking:

1. Use the Roslyn Analyzers. But this requires targeting net7.0+ because the System.* APIs weren't all attributed until then (and some still aren't). We can have a "special build" that only targets net7.0 during CI, but honestly I think that is super complicated and I haven't done that or recommended it.
2. Following https://learn.microsoft.com/en-us/dotnet/core/deploying/trimming/prepare-libraries-for-trimming#show-all-warnings-with-sample-application is the path I like because it also checks all your dependencies as well, and it doesn't require targeting a newer TFM. You can keep targeting the older ones, like netstandard2.0, and only the "test app" targets the latest TFM.
   • Following that path, looks something like this (the changes under the test folder).
   • That test takes ~30 seconds on a typical machine. It is taking about 1 minute on really slow CI machines.
   • For StackExchange.Redis, on my 2019 machine doing a clean publish like that takes 28 seconds.

Any thoughts on those options?

[eerhardt]

I'm not sure the CI failures are caused by me. But I can't really tell what failed. The Windows leg passed, so that makes me think it isn't my code.