Attempting to fix CI for ARM Mac and older dotnet format tool compatbility

[eli-iser]

Current CI builds fail. There are a few issues that this PR attempts to resolve:

• Tests on macos-latest fail with You can resolve the problem by installing the 'X64' .NET.. This is due to macos-latest being an ARM based runner, and .NET Standard 2.0/.NET 5 only supports x64. I moved to macos-13 which appears to be the latest version still using Intel CPUs. Note that macos-11 is being deprecated on 6/28/2024 so we should have some time yet with macos-13 to upgrade the SDK to support ARM build.
• Linter fails because the --fix- commands are not supported in dotnet format 6 and above. I pinned the version to 5 that still supports them. Ideally we'd want to see how to configure the latest format tool to do what we want, but for a quick fix/test I'm trying the "original" version. This also required moving from dotnet format (which always ran the latest version) to dotnet-format (which did run the correct version that was installed).
• Code coverage report uploading were missing the Codecov token to allow them to be uploaded. I've added the token to the GitHub secrets and reference it here.

Also updated the contribution doc with the above dotnet format version and removed the Stone generation section as it is no longer supported (instead being handled by the Spec Update action).

Checklist

General Contributing

• Have you read the Code of Conduct and signed the CLA?

Is This a Code Change?

• Non-code related change (markdown/git settings etc)
• SDK Code Change
• Example/Test Code Change

Validation

• Does this code build successfully?
• Do all tests pass?
• Does Stylecop pass?

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 47.89%. Comparing base (c6415d8) to head (cfbe93c).
Report is 4 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #360      +/-   ##
==========================================
- Coverage   51.33%   47.89%   -3.44%     
==========================================
  Files          14       17       +3     
  Lines        1422     1570     +148     
  Branches        0      137     +137     
==========================================
+ Hits          730      752      +22     
- Misses        692      776      +84     
- Partials        0       42      +42     

Flag	Coverage Δ
integration	44.77% <ø> (-2.84%)	⬇️
unit	9.42% <ø> (-1.83%)	⬇️

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