• When using managed mode, setting enabled: false now no longer fails buf generate
  and instead prints a warning log and ignores managed mode options.
• Add csharp_namespace option to managed mode, allowing except, which excludes
  modules from managed mode, and override, which specifies csharp_namespace values
  per module, overriding the default value. By default, when managed mode is enabled,
  csharp_namespace is set to the package name with each package sub-name capitalized.
• Promote buf convert to stable, keep buf beta convert aliased in the beta command.
• Add Types filter to buf generate command to specify types (message, enum,
  service) that should be included in the image. When specified, the resulting
  image will only include descriptors to describe the requested types.