[G-API]: Add Fluid bitwise operations implementation for (GMat, GScalar)
* Added Fluid `bitwise` with `Scalar` + acc.tests
- simple loop implementation for Fluid used (no `hal`);
- `Scalar` is casted to `int` in the beginning
- tests just modified to work with `Scalar`
- expected output in operators' tests fixed (operators can't change Mat's depth)
- `float` `Scalar` `RNG` added, `RNG` reworked (`time` is used now), initialization of test fixtures reworked
- if input or output is `float` Scalar is initialized by `float`
- some problems with Fluid/OCV floating-point comparison difference stashed by `AbsSimilarPoints()` usage, FIXME added
- divide-by-zero is now fixed differently and everywhere
* - Added perf_tests for bitwise_Scalar operations
- due to errors of Fluid floating-point comparison operations, added support of different validation in Cmp perf_tests; added FIXME
- reworked integral initialization of Scalar
* Addressing comments
- NULL -> nullptr
- Scalar convertion moved to the function
- avoid -> avoiding
* Addressing comments
* CV_assert -> GAPI_assert
* Addressed DM comments
- refactored convertScalarForBitwise()
- removed unnecessary braces for switch
* Changed the operators tests
- switch via `enum` implemented
- infrastructure for that refactored
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