Refactor common elements (error and status panels) out of TitledComponentBase subclasses and into TitledComponentBase itself.
Refactor common elements (error and status panels) out of TitledComponentBase subclasses and into TitledComponentBase itself.

Add SubtabBase as a new subclass of TitledComponentBase which implements a body panel with tabs.  Remember selected tabs in browser history so that the user doesn't lose tab context when using back & forward.

Make SummaryBase a subclass of SubtabBase rather than TitledComponentBase, so that WorkflowDetails and StateDetails can take advantage of the new tab features.

Add PropertiesTab, which implements our current PHP properties tab functionality plus browser history support.

[git-p4: depot-paths = "//depot/nimbus/integrations/EC-Gerrit/main/": change = 47503]

electric-cloud/EC-Gerrit,electric-cloud/EC-Gerrit,electric-cloud/EC-Gerrit