ui: bulk actions: rework filters and include tags

ui: bulk actions: rework filters and include tags

This moves the filters out of the grid header for the BulkActions and
puts them into their own fieldset above the grid. With that, we can
easily include a tags filter (one include and one exclude list).

The filter fieldset is collapsible and shows the active filters in
parenthesis. aside from that the filter should be the same as before.

To achieve the result, we regenerate the filterFn on every change of
every filter field, and set it with an 'id' so that only that filter is
overridden each time.

To make this work, we have to change three tiny details:
* manually set the labelWidths for the fields, otherwise it breaks
  the ones in the fieldset.
* change the counting in the 'getErrors' of the VMSelector, so that we
  actually get the count of selected VMs, not the one from the
  selectionModel
* override the plugins to '' in the BulkAction windows, so that e.g. in
  the backup window we still have the filters in the grid header
  (we could add a filter box there too, but that is already very crowded
  and would take up too much space for now)

Signed-off-by: Dominik Csapak <d.csapak@proxmox.com>