Add support for building CoreCLR for MacCatalyst/iOS simulator

[filipnavara]

Re-open and rebase of #98127

Build instructions:

• Build the runtime pack and tools: ./build.sh clr+clr.runtime+libs+packs -os [iossimulator/maccatalyst] -arch [x64/arm64] -cross -c Release
• Run the sample app: ./dotnet.sh publish src/mono/sample/iOS/Program.csproj -c Release /p:TargetOS=maccatalyst /p:TargetArchitecture=arm64 /p:DeployAndRun=true /p:UseMonoRuntime=false /p:RunAOTCompilation=false /p:MonoForceInterpreter=false

Related work:

• Counter-part Xamarin changes needed to build full workload and run MAUI apps: https://github.com/xamarin/xamarin-macios/pull/21627 / https://github.com/xamarin/xamarin-macios/compare/net8.0...filipnavara:xamarin-macios:net8.0-coreclr-ioslike?expand=1
• SDK would need to be updated with RIDs in KnownRuntimeFramework to use this
• tvOS support is dropped in this version of the PR. The OS doesn't expose Mach exceptions and it would need larger modification in the runtime to add the support.
• We don't use the new JIT API (https://github.com/dotnet/runtime/issues/108423). That's orthogonal problem but would be a necessity to support MacCatalyst/arm64 in production.

Notably, this doesn't include CI scripts to build this or the runtime packs. I am open to suggestions on how to better split this into more digestible/reviewable chunks.

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