[TASK] Possibility to disable grouping in workspace module

The workspace modules uses the ExtJS component GroupingStore
per default to group and nest version by page path. However,
this behavior get unhandy if all versions of all pages shall
be sorted by a particular column.

A new checkbox "group by path" shall be added to the top
columns menu to individually disable/enable this behavior.
Changes to that state are stored with the preferences of
a backend user for the accordant workspace.

Resolves: #60037
Releases: 6.2, 6.3
Change-Id: I8e9a2f3f14870c90ea5988a0182a54b22762390e