Merge pull request #17851 from anton-potapov:sole_tbb_executor

Merge pull request #17851 from anton-potapov:sole_tbb_executor

* TBB executor for GAPI

 - the sole executor
 - unit tests for it
 - no usage in the GAPI at the momnet

* TBB executor for GAPI

 - introduced new overload of execute to explicitly accept tbb::arena
   argument
 - added more basic tests
 - moved arena creation code into tests
 -

* TBB executor for GAPI

 - fixed compie errors & warnings

* TBB executor for GAPI

 - split all-in-one execute() function into logicaly independant parts

* TBB executor for GAPI

 - used util::variant in in the tile_node

* TBB executor for GAPI

 - moved copy_through_move to separate header
 - rearranged details staff in proper namespaces
 - moved all implementation into detail namespace

* TBB executor for GAPI

 - fixed build error with TBB 4.4.
 - fixed build warnings

* TBB executor for GAPI

 - aligned strings width
 - fixed spaces in expressions
 - fixed english grammar
 - minor improvements

* TBB executor for GAPI

 - added more comments
 - minor improvements

* TBB executor for GAPI

 - changed ITT_ prefix for macroses to GAPI_ITT

* TBB executor for GAPI

 - no more "unused" warning for GAPI_DbgAssert
 - changed local assert macro to man onto GAPI_DbgAssert

* TBB executor for GAPI

 - file renamings
 - changed local assert macro to man onto GAPI_DbgAsse

* TBB executor for GAPI

 - test file renamed
 - add more comments

* TBB executor for GAPI

 - minor clenups and cosmetic changes

* TBB executor for GAPI

 - minor clenups and cosmetic changes

* TBB executor for GAPI

 - changed spaces and curly braces alignment

* TBB executor for GAPI

 - minor cleanups

* TBB executor for GAPI

 - minor cleanups