[SystemConfiguration] Add support for xcode13 beta4.

[mandel-macaque]

The todo in MacCatalyst are the ignored in macOS, how did I find out:

# sort todo and ignore
sort -o macOS-SystemConfiguration.sorted macOS-SystemConfiguration.ignore
sort -o MacCatalyst-SystemConfiguration.sorted MacCatalyst-SystemConfiguration.todo
# compare sorted files
comm -1 -2  MacCatalyst-SystemConfiguration.sorted macOS-SystemConfiguration.sorted >> MacCatalyst-SystemConfiguration.ignore

Results in the added ignore and an empty .todo. I added the ignore sorted to make comparing easier.

[vs-mobiletools-engineering-service2]

❌ [PR Build] Tests failed on Build ❌

Tests failed on Build.

• Azure DevOps
• Html Report (VSDrops)

API diff

✅ API Diff from stable

View API diff

• iOS vsdrops gist
• macOS vsdrops gist
• macCat vsdrops gist
• macCatiOS gist
• tvOS vsdrops gist
• watchOS vsdrops gist

API & Generator diff

✅ API Diff (from PR only) (no change)
✅ Generator Diff (only version changes)

GitHub pages

Results can be found in the following github pages (it might take some time to publish):

• Test results
• API diff
• API & Generator diff

Test results

1 tests failed, 90 tests passed.

Failed tests

• introspection/Mac Catalyst/Debug [dotnet]: TimedOut (Execution timed out after 1200 seconds.
  No test log file was produced)

Pipeline on Agent XAMBOT-1094.BigSur'
Merge 410214d into ae77aed

[mandel-macaque]

Un related issue: https://github.com/xamarin/maccore/issues/2414