Add dynamic lapack/openblas lib loading at runtime

[multiphaseCFD]

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Context:

Switch static LAPACK linking to dynamic loading to LAPACK/OpenBLAS.

Description of the Change:

Deprecated static linking against lapack-dev. Now we load openblas libs deployed by scipy for Hermitian decomposition at runtime.

There are two different approaches for scipy.libs search depending on how users use/install lightning

• Build from source for C++: The C++ backend check the SCIPY_LIBS_PATH macro variable, which is configured at the compile time with the help of CMAKE and its built-in variable ${Python_SITELIB} .
• Wheels or pip -e . install: if SCIPY_LIBS_PATH doesn't work, we try to use dladdr to get the path\ to\ lightning_qubit_ops.so and we can get \path\to\scipy.libs with path\ to\ lightning_qubit_ops.so\..\..\scipy.libs, given that both scipy and lightning are installed in the same site-packages (which should be always true if the env is set up correctly).

Benefits:

The licence issue of linking against lapack-dev can be avoided.

Possible Drawbacks:

Related GitHub Issues:

[maliasadi]

Thanks @multiphaseCFD!

[multiphaseCFD]

Thanks @multiphaseCFD!

Thanks @maliasadi ! According to previous tests, removing the dummy file config.h could lead to failures in wheels building or C++ unit tests. Let's wait and see if there is a failure caused by removing config.h.

[maliasadi]

🥳

[dime10]

Great work! :)