[RFE] Support importing zip files

Currently you cannot import a zip file:

```
$  lvctl import -namespace jorti -id 123456789 -file  must-gather.local.1977146784160175632.zip
F1122 09:46:44.097430   27523 import.go:22] failed to validate import params: must gather file name must be a .tar.gz file
```

Supporting zips directly will remove the necessity of re-packing the must-gather.