The io/ioutil package has been deprecated as of Go 1.16 [1]. This commit
replaces the existing io/ioutil functions with their new definitions in
io and os packages.
Reference: https://golang.org/doc/go1.16#ioutil
Signed-off-by: Eng Zer Jun <engzerjun@gmail.com>
Otherwise it would log warnings about an empty file.
```
stores.go:138: store.NewFileStore("/tmp/3777352782"): file empty; treating it like a missing file [warning]
```
Signed-off-by: Maisem Ali <maisem@tailscale.com>
Also move KubeStore and MemStore into their own package.
RELNOTE: tsnet now supports providing a custom ipn.StateStore.
Signed-off-by: Maisem Ali <maisem@tailscale.com>
Eng Zer Jun
Brad Fitzpatrick
Maisem Ali