Lazy load for popup widgets

[Dergash]

This PR introduces lazy load for certain types of widgets (PopupWidgetTypes at the moment, but can be extended later), i.e. the data and row meta will not be fetched until those widgets are explicitly opened through showViewPopup dispatch.
If lazy widget shares business component with some non-lazy widget (either directly or through ancestors chaing), than it continues to be fetched.

1. A lot of efforts are directed into refactoring bcFetchDataEpic which tends to be overbloated with various loosely connected functionality: hierarchies, pagination, cancellation, cursors change, data fetch, row meta fetch, children fetch... Unit tests and tsdoc coverage should document current behavior
2. Efforts are made to make all five possible actions for this epic to work with widgetName instead of bcName prone to collisions. Work in progress.
3. <PickListField /> and <MultivalueField /> no longer show spinners while row meta for their corresponding business components if fetched; it was an ad hoc protection to prevent fetching data on popup open when the initial data is still fetched. With lazy load there is no initial fetch => no race condition, though it is still possible in a case when multiple popup fields share the same business component. Probably there is still work to do here.
4. WidgetMeta now has url field (it was always there, just missing from the interface)
5. As we still did not update redux-observable to 1.*.* due to backward-compatibility support, tests for Observable.race are omitted and epic implementations return flows intended to check manually

[Dergash]

/alpha

[coveralls]

Pull Request Test Coverage Report for Build 577916040

• 87 of 98 (88.78%) changed or added relevant lines in 7 files are covered.
• 2 unchanged lines in 2 files lost coverage.
• Overall coverage increased (+0.4%) to 61.517%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
src/components/InlinePickList/InlinePickList.tsx	0	2	0.0%
src/components/PickListField/PickListField.tsx	1	3	33.33%
src/epics/data/bcFetchData.ts	70	77	90.91%

Files with Coverage Reduction	New Missed Lines	%
src/components/InlinePickList/InlinePickList.tsx	1	26.42%
src/components/PickListField/PickListField.tsx	1	63.64%

Totals
Change from base Build 577717076:	0.4%
Covered Lines:	3281
Relevant Lines:	4676

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💛 - Coveralls