zip: Add fs.FS support for Go 1.16+

[klauspost]

Change writer api to match stdlib as well.

func (w *Writer) Copy(name string, src *File) error is changed to func (w *Writer) Copy(src *File) error to match the stdlib.

[orijbot]

Visit https://dashboard.github.orijtech.com?back=0&pr=432&remote=false&repo=klauspost%2Fcompress to see benchmark details.

[odeke-em]

Well done @klauspost, improvements for the benchmarks you care about https://dashboard.github.orijtech.com/benchmark/c099d0acb095438bb5590e89b746a405 :-)

If I may kindly ask, for notifications, would you like a comment for every commit telling you when it completed? Or would you prefer the Github Actions style notification that you have to proactively look at for completion on the PR's page? /cc @cuonglm @kirbyquerby

[klauspost]

@odeke-em Yeah. This seems like a good example of non-changes yielding rather big fluctuations. None of the benchmarks are affected by the code change in this PR. Kind of frustrating that the Go compiler has so big variance in compiles.

I definitely would like a notification. If possible with a table. Some systems like this will delete previous results when results from a new push arrives. That would be great so history doesn't get too cluttered with outdated benchmarks.

/cc @cuonglm @kirbyquerby

[saracen]

% go version 
go version go1.13.8 darwin/amd64

% go mod tidy
...
	github.com/klauspost/compress/zip imports
	io/fs: malformed module path "io/fs": missing dot in first path element

It looks like go mod tidy doesn't take into consideration build tags. This is a problem for us, as we use go mod tidy on the CI to ensure consistency.

@klauspost I don't expect there's anything that can be done about this, but figured I'd leave this here for anybody else that stumbles across this problem.

[klauspost]

@saracen Minimum supported Go version is currently Go 1.15 - could you check on that?

[saracen]

@klauspost That does appear to work. I figured the same thing would happen as io/fs was only introduced in go1.16. Apologies for the noise!