Remove unused files from GitHub runners

Remove unused files from GitHub runners

Majority of the software installed by default in GitHub runners is
irrelevant to OpenZFS. Reclaimed space could be used for more/bigger
vdev files. File deletion happens in the background, leveraging
`systemd-run` - the workflow is not significantly slowed down.

Before
```
Filesystem      Size  Used Avail Use% Mounted on
/dev/root        84G   53G   31G  63% /
```

After
```
Filesystem      Size  Used Avail Use% Mounted on
/dev/root        84G   15G   70G  18% /
```

Reviewed-by: George Melikov <mail@gmelikov.ru>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Ahelenia Ziemiańska <nabijaczleweli@nabijaczleweli.xyz>
Signed-off-by: szubersk <szuberskidamian@gmail.com>
Closes #13066