[vm] Clear native flag on dynamic invocation forwarders.
[vm] Clear native flag on dynamic invocation forwarders.

When creating a dynamic invocation forwarder, the VM clones the original
function object and then modifies the clone to create the forwarder.
Previously, the is_native flag was left untouched, but now it is
properly cleared.

Change-Id: I133ffdc0d0d3d727f7b7e47af22944e6b0574ee7
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/110721
Reviewed-by: Martin Kustermann <a35dd5b79fac84b2bb3b026a16b8becc55af5961@google.com>
Commit-Queue: Teagan Strickland <cce218d042444252b7ac446d60910fca7732559c@google.com>

dart-archive/dart-sdk,dart-lang/sdk,dart-archive/dart-sdk,dartino/dart-sdk,dartino/dart-sdk,dart-lang/sdk,dartino/dart-sdk,dart-archive/dart-sdk,dart-lang/sdk,dart-lang/sdk,dartino/dart-sdk,dart-archive/dart-sdk,dartino/dart-sdk,dartino/dart-sdk,dartino/dart-sdk,dart-lang/sdk,dartino/dart-sdk,dart-archive/dart-sdk,dart-archive/dart-sdk,dart-lang/sdk,dartino/dart-sdk,dart-archive/dart-sdk,dart-archive/dart-sdk,dart-archive/dart-sdk,dart-lang/sdk,dart-lang/sdk