This is to cover the common pattern: open->read/write->close,
where SetAttr needs to be called to update atime/mtime before
the file is closed.
Benchmark results:
BM_OpenReadClose/10240 CPU
setattr+clunk: 63783 ns
VFS2: 68109 ns
VFS1: 72507 ns
Updates #1198
PiperOrigin-RevId: 329628461