Merge pull request #12990 from rgarnov:gapi_fluid_reshape_support

G-API: Introduce new `reshape()` API (#12990)

* Moved initFluidUnits, initLineConsumption, calcLatency, calcSkew to separate functions

* Added Fluid::View::allocate method (moved allocation logic from constructor)

* Changed util::zip to util::indexed, utilized collectInputMeta in GFluidExecutable constructor

* Added makeReshape method to FluidExecutable

* Removed m_outputRoi from GFluidExecutable

* Added reshape feature

* Added switch of resize mapper if agent ratio was changed

* Added more TODOs and renamed a function

* G-API reshape(): add missing `override` specifiers

Fix warnings on all platforms

modules/gapi/include/opencv2/gapi/fluid/gfluidbuffer.hpp

@@ -105,7 +105,7 @@ public:
 
     const GMatDesc& meta() const;
 
-    View mkView(int lineConsumption, int borderSize, BorderOpt border, bool ownStorage);
+    View mkView(int borderSize, bool ownStorage);
 
     class GAPI_EXPORTS Priv;      // internal use only
     Priv& priv();               // internal use only

modules/gapi/include/opencv2/gapi/gcompiled.hpp

@@ -50,6 +50,9 @@ public:
     const GMetaArgs& metas() const; // Meta passed to compile()
     const GMetaArgs& outMetas() const; // Inferred output metadata
 
+    bool canReshape() const; // is reshape mechanism supported by GCompiled
+    void reshape(const GMetaArgs& inMetas, const GCompileArgs& args); // run reshape procedure
+
 protected:
     std::shared_ptr<Priv> m_priv;
 };