V0.21.0 master merger

[mlxd]

Context: Add changes from v0.21.0_rc0 branch into master

Description of the Change:

Benefits:

Possible Drawbacks:

Related GitHub Issues:

[codecov]

Codecov Report

Merging #233 (b3c534e) into master (2d2df24) will not change coverage.
The diff coverage is 100.00%.

❗ Current head b3c534e differs from pull request most recent head a556147. Consider uploading reports for the commit a556147 to get more accurate results

@@           Coverage Diff           @@
##           master     #233   +/-   ##
=======================================
  Coverage   99.70%   99.70%           
=======================================
  Files           4        4           
  Lines         344      344           
=======================================
  Hits          343      343           
  Misses          1        1           

Impacted Files	Coverage Δ
pennylane_lightning/_version.py	100.00% <100.00%> (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 2d2df24...a556147. Read the comment docs.

[github-actions]

Test Report (C++) on Ubuntu

       1 files  ±0         1 suites  ±0   0s ⏱️ ±0s
   555 tests ±0     555 ✔️ ±0  0 💤 ±0  0 ❌ ±0 
2 289 runs  ±0  2 289 ✔️ ±0  0 💤 ±0  0 ❌ ±0 

Results for commit a556147. ± Comparison against base commit 2d2df24.

♻️ This comment has been updated with latest results.

[mlxd]

Hi all, this merges in some of the previous changes to the last release that haven't yet touched master. Feel free to let me know if anything is amiss.

[chaeyeunpark]

Looks good to me! (first time to use this phrase 😄 )

[maliasadi]

Happy to approve!

[AmintorDusko]

Nice work!

[mlxd]

Thanks all!