mgr/dashboard: add columns to Pools table

mgr/dashboard: add columns to Pools table

* Added columns:
Usage, Read bytes, Write bytes, Read ops, Write ops.

* TableKeyValueComponent:
Bugfix in method: _insertFlattenObjects

* Updated jest global mock:
Now window.getComputedStyle returns an object
that has getPropertyValue defined
(otherwise jest pool tests involving chart.js threw error). See:
https://developer.mozilla.org/en-US/docs/Web/API/Window/getComputedStyle

Fixes: https://tracker.ceph.com/issues/37717
Fixes: https://tracker.ceph.com/issues/34320
Signed-off-by: Alfonso Martínez <almartin@redhat.com>