Fix handling of "no-cpp" test tag for error tests, where "cpp" is already removed from the list of test backends.

Closes #3575

Disable GC during hacked calls to PyType_Ready() that simulate a heap type for an actual non-heap type, because it can lead to crashes if GC visits such a hacked type.
Closes https://github.com/cython/cython/issues/3603

Also mark the case of an uninitialised memory view slice as "unlikely()" when refcounting it since it's most probably not a performance critical case.

Mark the last deletion of a memory view slice as "unlikely()" to ask the C compiler to optimise for the repeated re-use case (usually in loops).

Mark the first creation of a memory view slice as "unlikely()" to ask the C compiler to optimise for the repeated re-use case (usually in loops).

Fix up the NumPy warnings hack by using the actual "import_array()" function declaration instead of a wrong one.

Closes https://github.com/cython/cython/issues/3594

Closes https://github.com/cython/cython/issues/1462

Move the work directory of the examples tests into an 'examples/' subdirectory to get it out of the way of the other test types.

Make sure the module init function is declared as 'extern "C"' in C++ also when the CYTHON_NO_PYINIT_EXPORT option is used.
Closes #3414.

Closes #3038.

Fix optimisation of aligned '%' formats ('%05s', '%-5s') into the correct f-string alignment format.
Closes https://github.com/cython/cython/issues/3476

Floats do not support '{x:d}' formatting and need conversion to 'int' first.
Closes https://github.com/cython/cython/issues/3092