Remove PI gates implementation

[maliasadi]

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Context:

Description of the Change:

Benefits:

Possible Drawbacks:

Related GitHub Issues:
[sc-73507]

[multiphaseCFD]

Thanks @maliasadi ! LGTM.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 94.22%. Comparing base (8796bab) to head (3ffa46e).
Report is 1 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #925      +/-   ##
==========================================
- Coverage   94.98%   94.22%   -0.76%     
==========================================
  Files          95      165      +70     
  Lines       13175    20533    +7358     
==========================================
+ Hits        12514    19348    +6834     
- Misses        661     1185     +524     

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[AmintorDusko]

WOW beautiful!

[AmintorDusko]

Please test also the wheels.

[LuisAlfredoNu]

Looks very nice, this will speed up the compilation time. Thank you @maliasadi
Just a couple of comments

[LuisAlfredoNu]

Thank you @maliasadi
Nice work!

Just one question. Why do we remove the GateImplementationsPI?

[LuisAlfredoNu]

Another question. Do the other devices (LK and LGPU) have the GateImplementationsPI? 🤔

[multiphaseCFD]

Nice job! Thanks @maliasadi.

[maliasadi]

Thanks for your review @LuisAlfredoNu!

Just one question. Why do we remove the GateImplementationsPI?

The PI gates were the first implementation of gate kernels in "lightning.qubit" using pre-computed indices, prior to the development of LM (less memory) and AVX kernels. We shouldn't use these kernels, as LM kernels are faster than PI gates for all 'supported' gates and are now our base kernels across different platforms or they should be on macOS ;) thus, we can deprecate them without any performance penalty in favour of reducing compilation time and ensuring that we only rely on LM kernels in the dynamic dispatcher across all platforms.

Another question. Do the other devices (LK and LGPU) have the GateImplementationsPI? 🤔

No, LK follows LM kernel design and LGPU is backed by custatevec.