Improve trimming support for EF Core apps to reduce application size

[roji]

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ILLinker allows making application size smaller by trimming code that isn't actually used. This is problematic in various dynamic/reflection scenarios, where the linker is unable to know that a method is actually needed.

Done in 8.0

• Allow stripping away all model building code to reduce application size #29755

Backlog

• When looking up methods via reflection, be trimming/AOT-friendly #26288
• Stop eagerly loading methods/members via reflection which aren't necessarily needed #27113
• Specifically check SQLite (i.e. the native dependency thing)
• Add feature switches to reduce app size #24901
• Allow stripping away the 1st part of the query pipeline to reduce application size #29762
• Consider removing the partial trimming annotations introduced in EF Core 7.0 #29763

Resources:

• .NET documentation on preparing libraris for trimming
• App Trimming in .NET 5
• Customizing Trimming in .NET 5

FYI the regression testing strategy for this isn't trivial
Relevant blog post: https://devblogs.microsoft.com/dotnet/app-trimming-in-net-5/

[hez2010]

I think the implementation of this method need to be revisited:

efcore/src/Microsoft.Data.Sqlite.Core/Utilities/BundleInitializer.cs

Line 20 in b3619b4

assembly = Assembly.Load(new AssemblyName("SQLitePCLRaw.batteries_v2"));

Why not call SQLitePCL.Batteries_V2.Init() directly?

[AndriySvyryd]

For .NET 6: https://docs.microsoft.com/en-us/dotnet/core/deploying/trimming/prepare-libraries-for-trimming

[AndriySvyryd]

Also take dotnet/runtime#61231 into account.
https://github.com/hez2010/EFCore.NativeAOT is a sample app that shows the common things that need to be configured.
c651888 contains our initial stab at this