archive/zip: preallocate fileList size for Reader.Open
When building the index of file entries for Reader.Open (when the Reader
is used as an io/fs.FS), reduce reallocations by pre-allocating the
count of entries based on the count of file entries.
Change-Id: I05048337cb5e752054b3e984a8a5ec5199c4589b
Reviewed-on: https://go-review.googlesource.com/c/go/+/655476
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com> Reviewed-by: Ian Lance Taylor <iant@google.com> Reviewed-by: Junyang Shao <shaojunyang@google.com>
Auto-Submit: Ian Lance Taylor <iant@golang.org>