[DFSan] Handle fast16labels for all API functions.

Summary:
Support fast16labels in `dfsan_has_label`, and print an error for all
other API functions.

Reviewers: kcc, vitalybuka, pcc

Reviewed By: kcc

Subscribers: jfb, llvm-commits, #sanitizers

Tags: #sanitizers

Differential Revision: https://reviews.llvm.org/D84215