Pin macos test runners to macos-12

[mikealfare]

Problem

macos-latest now points to macos-14-arm64; it used to point to macos-12. There is no py39 nor py38 on macos-14-arm64.

Solution

Pin to macos-12 for now and discuss long term options to use macos-14-arm64, and CI pinning in general.

Checklist

• I have read the contributing guide and understand what's expected of me
• I have run this code in development and it appears to resolve the stated issue
• This PR includes tests, or tests are not required/relevant for this PR
• This PR has no interface changes (e.g. macros, cli, logs, json artifacts, config files, adapter interface, etc) or this PR has already received feedback and approval from Product or DX

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 88.14%. Comparing base (1e4bed0) to head (7120075).

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #10031      +/-   ##
==========================================
- Coverage   88.16%   88.14%   -0.02%     
==========================================
  Files         181      181              
  Lines       22643    22643              
==========================================
- Hits        19963    19959       -4     
- Misses       2680     2684       +4     

Flag	Coverage Δ
integration	85.44% <ø> (-0.02%)	⬇️
unit	62.31% <ø> (ø)

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[emmyoop]

let's test with py-3.11 on macos

[github-actions]

The backport to 1.6.latest failed:

The process '/usr/bin/git' failed with exit code 1

To backport manually, run these commands in your terminal:

# Fetch latest updates from GitHub
git fetch
# Create a new working tree
git worktree add .worktrees/backport-1.6.latest 1.6.latest
# Navigate to the new working tree
cd .worktrees/backport-1.6.latest
# Create a new branch
git switch --create backport-10031-to-1.6.latest
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick -x --mainline 1 bcbde3ac4204f00d964a3ea60896b6af1df18c71
# Push it to GitHub
git push --set-upstream origin backport-10031-to-1.6.latest
# Go back to the original working tree
cd ../..
# Delete the working tree
git worktree remove .worktrees/backport-1.6.latest

Then, create a pull request where the base branch is 1.6.latest and the compare/head branch is backport-10031-to-1.6.latest.