"filter with cell value" context menu option

It would be nice to have a shortcut for filtering a column by the value of a cell.

This is a very common operation, but right now it takes at least 3 steps to filter a column by a given value (that is present in a cell in the table view).

- right click cell > copy cell
- right click column header > filter
- paste value, enter

A context menu option for the cell like "filter with cell value" that:
- sets the filter column
- sets the operator to equals
- enters the cell value in the search field
- sets the keyboard-focus to the search field (or just applies the filter immediately)

If the cell contains a `NULL` value the operator should be set to `IS NULL`

Start by locating the table-view cell context menu and the existing column-filter flow. Add the requested "filter with cell value" action, including equals for ordinary values and IS NULL for NULL cells, then verify that the column, search field, focus or immediate application behave as described.

Written by the indexing model from the issue text.