Add test coverage for LKokkos

[vincentmr]

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---

Context:
The LKokkos backend has lower coverage than PennyLane and LQubit. Codecov oftentimes fails as LKokkos' coverage does not meet the target.

Description of the Change:

• Add tests, parametrization with GENERATE (gate inverse in particular to target the inverse branch of functors), etc.
• Enums defined in GateOperation.hpp start at 1 (previously 0). ::BEGIN is introduced in a few places where it was assumed 0 accordingly.
• Enable pre-commit hooks to format all Python files and linting of all Python source files.

Benefits:
Better test coverage.

Possible Drawbacks:

Related GitHub Issues:

[codecov]

Codecov Report

Patch coverage: 100.00% and project coverage change: +6.02% 🎉

Comparison is base (869bbb8) 93.04% compared to head (3d0d6ce) 99.07%.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #485      +/-   ##
==========================================
+ Coverage   93.04%   99.07%   +6.02%     
==========================================
  Files         142      142              
  Lines       16278    16485     +207     
==========================================
+ Hits        15146    16332    +1186     
+ Misses       1132      153     -979     

Files Changed	Coverage Δ
...s/lightning_kokkos/measurements/ExpValFunctors.hpp	100.00% <ø> (+43.06%)	⬆️
...ghtning_kokkos/measurements/MeasurementsKokkos.hpp	98.15% <ø> (+3.68%)	⬆️
...tning_qubit/gates/tests/Test_OpToMemberFuncPtr.cpp	18.46% <ø> (ø)
pennylane_lightning/core/_version.py	100.00% <100.00%> (ø)
.../simulators/lightning_kokkos/StateVectorKokkos.hpp	99.76% <100.00%> (+5.99%)	⬆️
...s/gates/tests/Test_StateVectorKokkos_Generator.cpp	100.00% <100.00%> (ø)
...os/gates/tests/Test_StateVectorKokkos_NonParam.cpp	100.00% <100.00%> (ø)
...okkos/gates/tests/Test_StateVectorKokkos_Param.cpp	100.00% <100.00%> (ø)
...asurements/tests/Test_StateVectorKokkos_Expval.cpp	100.00% <100.00%> (ø)
...surements/tests/Test_StateVectorKokkos_Measure.cpp	100.00% <100.00%> (ø)
... and 2 more

... and 8 files with indirect coverage changes

☔ View full report in Codecov by Sentry.
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[AmintorDusko]

I notice that you are excluding some parts from the coverage checks.
Could you please elaborate on why?

[mlxd]

Thanks @vincentmr

Just a few comments

[AmintorDusko]

You did a nice work so far.

[AmintorDusko]

Good work on that! I will approve it now, but please check if, without the coverage exclusion zone, we still pass the coverage checks. I think it is better not to add it, if not needed.

[mlxd]

Thanks @vincentmr