Enable code analyzers

[MihaZupan]

Brings in CodeAnalysis.src.globalconfig and CodeAnalysis.test.globalconfig from dotnet/runtime.

The config is the same, with the exception of

// Disabled because we still target .NET 6.0
SYSLIB1045: Convert to 'GeneratedRegexAttribute'.
CA1510: Use ArgumentNullException throw helper

// Disabled because it's too late / we don't care
CA1727: Use PascalCase for named placeholders
CA2007: Consider calling ConfigureAwait on the awaited task

// Disabled in tests
xUnit1004: Test methods should not be skipped