Before this change, returning a DefaultInfo obtained from a native rule target from a Starlark rule would lose the data_runfiles and
default_runfiles. This could only be worked around by creating a DefaultInfo provider instance in Starlark explicitly setting these
fields.

This is fixed by having the DelegatingDefaultInfo return null instead of an empty Runfiles object for the stateless runfiles, which indicates to addSimpleProviders in StarlarkRuleConfiguredTargetUtils that default and data runfiles should be used instead. Previously, this logic would only use the always empty stateless runfiles.

Fixes #9442.

Closes #14123.

PiperOrigin-RevId: 403921510