[Proposal]push delete on conditionnal clause

Hi,
We have need to purge some data in a given table according to a condition (where MyData>9999).

Currently, we can do that with
```console
$ lino pull --table MyTable --where 'MyData>9999' MyAliasDB | lino push delete --table MyTable MyAliasDB
```
Ideally we would have

```console
$ lino push delete --table MyTable --where 'MyData>9999' MyAliasDB
```
lino push delete with conditionnal must ignore input data
Thanks

Start by tracing the `lino push delete` command and its existing handling of the `--table` argument. Check how conditional input is currently processed, then implement the requested `--where 'MyData>9999'` form so it ignores piped input and deletes matching rows; verify the command against a representative table.

Written by the indexing model from the issue text.