[Enhancement] recsel all record types

[Avid Seeker]

Current workaround is (by <jemarch@gnu.org>):

```
for t in $(recinf -n db.rec); do recsel -t $t db.rec; echo ""; done
```

but it would be better and more efficient if this was implemented in the
program. Especially when user needs to add more complex queries.

Note that this might partially solve recutils cannot select non-typed (default) 
records:

https://www.gnu.org/software/recutils/manual/Selecting-by-Type.html#Selecting-by-Type