Bump deps

```
* use go 1.17 semantics in go.mod
* pin tonistiigi/fsutil dep to match docker/docker's dep
go get -u ./...
go mod vendor
```

vendor/github.com/vbatts/tar-split/tar/storage/getter.go

@@ -92,11 +92,12 @@ func NewDiscardFilePutter() FilePutter {
 }
 
 type bitBucketFilePutter struct {
+	buffer [32 * 1024]byte // 32 kB is the buffer size currently used by io.Copy, as of August 2021.
 }
 
 func (bbfp *bitBucketFilePutter) Put(name string, r io.Reader) (int64, []byte, error) {
 	c := crc64.New(CRCTable)
-	i, err := io.Copy(c, r)
+	i, err := io.CopyBuffer(c, r, bbfp.buffer[:])
 	return i, c.Sum(nil), err
 }