[UpdateTestChecks] Update tests option

Summary:
Port of new feature introduced https://reviews.llvm.org/D65610 to other update scripts.

- update_*_checks.py: add an alias -u for --update-only
- port --update-only to other update_*_test_checks.py scripts
- update script aborts if the test file was generated by another update_*_test_checks.py utility

Reviewers: lebedev.ri, RKSimon, MaskRay, reames, gbedwell

Reviewed By: MaskRay

Subscribers: llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D65793

llvm-svn: 368174