[mono][arm64] Fixed passing/receiving hfa structures with fixed buffers.

[UnityAlex]

Fixes dotnet/runtime#90423.

Cherrypicked from upstream. Pick was not clean and required some massaging.

• Should this pull request have release notes?
  • Yes
  • No
• Do these changes need to be back ported?
  • Yes
  • No
• Do these changes need to be upstreamed to mono/mono or dotnet/runtime repositories?
  • Yes
  • No (Cherrypicked from upstream)

Reviewers: please consider these questions as well! ❤️

Release notes

Fixed UUM-30210 @UnityAlex :
Mono: Fixed issue where a fixed buffer within a valuetype struct would not be passed by value correctly.

Backports
2023.1, 2021.3, 2022.2

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