[CoreMidi] Make P/Invokes have blittable signatures.

[rolfbjarne]

This turned into a rather involved exercise, because the
MidiThruConnectionParamsStruct struct had several array fields that needed
marshalling to work.

The changes include:

• Unwrap the array fields with MarshalAs attributes to be individual fields
  instead.
• Write a number of tests to ensure the changes work.
• Fix an overflow issue found by the tests for the Controls array if trying to
  set to an array with more than 65535 elements.
• Fix an overflow issue found by the tests for the Maps array if trying to set
  to an array with more than 65535 elements.
• Fix an issue found by the tests where we wouldn't deserialize the Maps array
  correctly from a byte array / NSData if the Maps array had more than 1
  element.
• Fix a consistency issue found in the tests where deserializing a serialized
  structure doesn't yield the same result.
  • In particular this happens with the ChannelMap property: behavior has
    changed a little bit where setting the ChannelMap to an array with fewer
    than 16 elements (including a null array) will not return the same array
    anymore, but instead an array with 16 elements, where the extra elements
    are all 0. I've also made the ChannelMap property non-nullable, since
    the nullability state isn't serializable into the underlying struct.

Contributes towards #15684.

[github-actions]

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[vs-mobiletools-engineering-service2]

🔥 [PR Build] Build failed 🔥

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[vs-mobiletools-engineering-service2]

🔥 Unable to find the contents for the comment: D:\a\1\s\change-detection\results\gh-comment.md does not exist :fire

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[vs-mobiletools-engineering-service2]

💻 [CI Build] Tests on macOS M1 - Mac Ventura (13.0) passed 💻

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[vs-mobiletools-engineering-service2]

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• xamarin.ios-17.1.0.302.pkg
• xamarin.mac-9.1.0.302.pkg

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💻 [CI Build] Windows Integration Tests passed 💻

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[vs-mobiletools-engineering-service2]

✅ API diff for current PR / commit

Legacy Xamarin (No breaking changes)

• iOS (no change detected)
• tvOS (no change detected)
• watchOS (no change detected)
• macOS (no change detected)

NET (empty diffs)

• iOS: (empty diff detected)
• tvOS: (empty diff detected)
• MacCatalyst: (empty diff detected)
• macOS: (empty diff detected)

✅ API diff vs stable

Legacy Xamarin (No breaking changes)

• iOS: vsdrops gist (No breaking changes)
• tvOS: vsdrops gist (No breaking changes)
• watchOS: vsdrops gist (No breaking changes)
• macOS: vsdrops gist (No breaking changes)

.NET (No breaking changes)

• iOS: vsdrops gist (No breaking changes)
• tvOS: vsdrops gist (No breaking changes)
• MacCatalyst: vsdrops gist (No breaking changes)
• macOS: vsdrops gist (No breaking changes)
• Microsoft.iOS vs Microsoft.MacCatalyst: vsdrops gist

Legacy Xamarin (stable) vs .NET

• iOS: vsdrops gist
• tvOS: vsdrops gist
• macOS: vsdrops gist

ℹ️ Generator diff

Generator Diff: vsdrops (html) vsdrops (raw diff) gist (raw diff) - Please review changes)

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[vs-mobiletools-engineering-service2]

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✅ All tests passed on VSTS: simulator tests.

🎉 All 235 tests passed 🎉

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✅ bcl: All 69 tests passed. Html Report (VSDrops) Download
✅ cecil: All 1 tests passed. Html Report (VSDrops) Download
✅ dotnettests: All 1 tests passed. Html Report (VSDrops) Download
✅ fsharp: All 7 tests passed. Html Report (VSDrops) Download
✅ framework: All 8 tests passed. Html Report (VSDrops) Download
✅ generator: All 2 tests passed. Html Report (VSDrops) Download
✅ interdependent_binding_projects: All 7 tests passed. Html Report (VSDrops) Download
✅ install_source: All 1 tests passed. Html Report (VSDrops) Download
✅ introspection: All 8 tests passed. Html Report (VSDrops) Download
✅ linker: All 65 tests passed. Html Report (VSDrops) Download
✅ mac_binding_project: All 1 tests passed. Html Report (VSDrops) Download
✅ mmp: All 2 tests passed. Html Report (VSDrops) Download
✅ mononative: All 6 tests passed. Html Report (VSDrops) Download
✅ monotouch: All 41 tests passed. [attempt 2] Html Report (VSDrops) Download
✅ msbuild: All 2 tests passed. Html Report (VSDrops) Download
✅ mtouch: All 1 tests passed. Html Report (VSDrops) Download
✅ xammac: All 3 tests passed. Html Report (VSDrops) Download
✅ xcframework: All 8 tests passed. Html Report (VSDrops) Download
✅ xtro: All 2 tests passed. [attempt 2] Html Report (VSDrops) Download

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[dalexsoto]

This is still haunting us in 2024 😅, LGTM amazing job Rolf!