MetaBackend

[BrunoLiegiBastonLiegi]

This PR implements a MetaBackend to load each qibojit backend and list the available ones.

[alecandido]

Minor comments. It looks perfect.

[alecandido]

In principle, you could even implement this with a dict. Or, even better, an Enum.

Suggested change

	if platform == "numba":
	return NumbaBackend()
	elif platform == "cupy":
	return CupyBackend()
	elif platform == "cuquantum":
	return CuQuantumBackend()
	else:
	raise_error(
	ValueError,
	f"Unsupported platform, please use one among {PLATFORMS}.",
	)
	return Platforms[platform].value()

and above, changing the constant to:

class Platforms(Enum):
    numpy = NumpyBackend
    ...

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 100.00%. Comparing base (df23518) to head (09448ce).

Additional details and impacted files

@@            Coverage Diff            @@
##              main      #172   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files           12        12           
  Lines         1085      1112   +27     
=========================================
+ Hits          1085      1112   +27     

Flag	Coverage Δ
unittests	100.00% <100.00%> (ø)

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[stavros11]

Approving so that you can merge if needed.