Add qchem gates and generators

[maliasadi]

Context:
This PR adds all unsupported parameterised gates and generators for adjoint-diff including,

• SingleExcitation,
• SingleExcitationPlus,
• SingleExcitationMinus,
• DoubleExcitation,
• DoubleExcitationPlus,
• DoubleExcitationMinus,

Benchmark:

[github-actions]

Hello. You may have forgotten to update the changelog!
Please edit .github/CHANGELOG.md with:

• A one-to-two sentence description of the change. You may include a small working example for new features.
• A link back to this PR.
• Your name (or GitHub username) in the contributors section.

[github-actions]

Test Report (C++) on Ubuntu

           1 files  ±    0             1 suites  ±0   0s ⏱️ ±0s
       854 tests +  90         854 ✔️ +  90  0 💤 ±0  0 ❌ ±0 
228 742 runs  +174  228 742 ✔️ +174  0 💤 ±0  0 ❌ ±0 

Results for commit d0c3d0c. ± Comparison against base commit b58394e.

♻️ This comment has been updated with latest results.

[codecov]

Codecov Report

Merging #289 (d0c3d0c) into master (b58394e) will increase coverage by 0.06%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master     #289      +/-   ##
==========================================
+ Coverage   99.18%   99.24%   +0.06%     
==========================================
  Files          28       29       +1     
  Lines        3060     3330     +270     
==========================================
+ Hits         3035     3305     +270     
  Misses         25       25              

Impacted Files	Coverage Δ
pennylane_lightning/_serialize.py	100.00% <ø> (ø)
...ennylane_lightning/src/gates/OpToMemberFuncPtr.hpp	100.00% <ø> (ø)
...ng/src/gates/cpu_kernels/GateImplementationsLM.hpp	100.00% <ø> (ø)
...ng/src/gates/cpu_kernels/GateImplementationsPI.hpp	100.00% <ø> (ø)
...nnylane_lightning/src/simulator/DefaultKernels.hpp	100.00% <ø> (ø)
pennylane_lightning/_version.py	100.00% <100.00%> (ø)
pennylane_lightning/lightning_qubit.py	100.00% <100.00%> (ø)
...src/gates/cpu_kernels/QChemGateImplementations.hpp	100.00% <100.00%> (ø)
...ennylane_lightning/src/gates/DynamicDispatcher.cpp	100.00% <0.00%> (ø)

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update b58394e...d0c3d0c. Read the comment docs.

[chaeyeunpark]

Thanks, @maliasadi for the great works! But can we merge this after my PR (#274) as it involves several changes in kernels?

[maliasadi]

Thanks, @maliasadi for the great works! But can we merge this after my PR (#274) as it involves several changes in kernels?

Sure thing @chaeyeunpark!

[chaeyeunpark]

Hi @maliasadi, I will review this PR when the changes in master are merged.

[chaeyeunpark]

Thanks, @maliasadi for amazing work! I just have a few questions.

[mlxd]

Awesome work @maliasadi
Nothing major to add, just a single question.

[chaeyeunpark]

Thanks, @maliasadi again for a great job! I just have one more question.

[isschoch]

Looks good. nice & clean code!