* fix: apply S3 Expiry Metadata
* add test Header X-Seaweedfs-Expires-S3
* resolve comments
* test entry lookup by mtime
* filer: skip s3 expiry stamp on versioned entries
The s3 expiry path skips entries carrying a version id, so stamping one
takes away its expiry rather than moving it onto mtime. Files under
.versions/ are written once, so crtime already tracks their needles.
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Co-authored-by: Konstantin Lebedev <whitefox@mayflower.work>
Co-authored-by: Chris Lu <chris.lu@gmail.com>
