When using builtin_openssl=ON, CMake erroneously exports the builtin
static libraries in ROOTConfig-targets.cmake, which causes problems with
dependent projects. In order to avoid this, we need Net and RHTTP to use
SSL as a private dependency. Since CMake requires target_link_libraries()
to either be all-plain (as before) or all-keyword (required to allow
PRIVATE linking), we need to move the build system to use all-keyword
linking only.

Fixes: ROOT-9532

Fix potential compilation error C2664: 'HANDLE CreateFileW(LPCWSTR,DWORD,DWORD,LPSECURITY_ATTRIBUTES,DWORD,DWORD,HANDLE)': cannot convert argument 1 from 'const char [8]' to 'LPCWSTR' with Unicode/MBCS, as reported here: https://github.com/root-project/cling/issues/186#issuecomment-404902026

This fixes the issue reported on the forum at: https://root-forum.cern.ch/t/windows-10-source-installation-failing-due-to-python-3-bindings/29771

Shows again same results as in the tutorials/dataframe/df101_h1Analysis.C
script.

In TGraph2D::GetHistogram when the points were all in the same plane (along X or Y) at a
negative coordinate, the computed axis limits were not correct. This was reported
here: https://root-forum.cern.ch/t/potential-bug-in-tgraph2d/29700/5.

Fixes ROOT-9526.

This is an alternative implementation of #2194. Changed Pythonize to
call Evaluate instead of doing Calc on code containing
cling::printValue.

Simplifies types, considerably.

Added test cases for forward and backward propagation through a single convolution layer in both architectures.

I had to revert the debugging mechanism to use the lower level `Print()` because `PrintMatrix` only works for the CPU case.

PassAsVec<N, T>(func) is a callable that takes N arguments of type T,
passes them to func as a collection (`func({v1, v2, ...}`) and returns
the result of the call to `func`.

This helper makes it possible to pass several columns of the same
type to a callable that accepts a vector of that type.

- moved internals from ROOT::Internal to ROOT::Internal::RDF
- removed useless includes

This reverts commit bf2cc576.

Fixed all tests to return status code - now CI will catch broken tests. Added tests for the CPU architecture