tweak otel-dotnet-auto-install.sh arch detection

[jrr]

Running the installer script on a mac, it prompts the user to manually specify architecture:

./otel-dotnet-auto-install.sh 
Set the architecture type using the ARCHITECTURE environment variable. Supported values: x64, arm64.

Why

The script is clearly designed to automatically detect architecture, it's just missing a case to handle MacOS' behavior.

What

Add a case for arm64 (alongside the existing aarch64)

Tests

With this change, the script completes successfully on my Mac.

Checklist

• CHANGELOG.md is updated.
• Documentation is updated.
• New features are covered by tests.

[linux-foundation-easycla]

• ❌ - login: @jrr / name: John Ruble . The commit (f44d2f4) is not authorized under a signed CLA. Please click here to be authorized. For further assistance with EasyCLA, please submit a support request ticket.

[jrr]

Meta-feedback - this is the most friction I've ever experienced on what should be an easy drive-by contribution. I'm not going to sign a contract with a mailing address for this one-line change. For what it's worth: nobody owns this IP and anyone is welcome to reproduce it!

[Kielek]

@jrr, thank for trying to improve this project.
It will be great if you can sign EasyCLA, it will allow us (and other OpenTelemetry projects) to accept your contributions.

This requirements is set up by the CNCF foundation, we are not allowed to make any exceptions related to this. As a project maintainers we do not have any access to the information you shared. Only status signed/non-signed is availabe through this tool.

[RassK]

I think it was originally aarch64 due that's the constant that Linux is using. AFAIK arm64 is used on MacOS and it wasn't supported that time. I don't remember if arm64 runs on mac now properly?

[Kielek]

Will be handled by changes in #4516. Closing.
Feel free to reopen if you are fine with singing CLA.