zapslog stabilization tracking issue

This issue tracks everything we need to do before zapslog can be moved to the main go.uber.org/zap module.

• #1329
• #1334
• zapslog: Ensure adequate test coverage
• #1337
• zapslog: Add a zapslog.Core that writes Zap logs to a slog.Handler Skip given https://github.com/uber-go/zap/issues/1333#issuecomment-1930389149
  • We may want to rename zapslog.Options to HandlerOptions when we do this.
• #1270

Future features: Things we can add to it without risk after the initial availability:

• #1412