Fix tests for msvc

[chaeyeunpark]

Currently, MSVC does not compile the test executable. This PR enables MSVC to compile the tests and fix some errors/warnings from MSVC.

Also closes #263

[github-actions]

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[codecov]

Codecov Report

Merging #264 (a27c8a4) into master (368b2bb) will not change coverage.
The diff coverage is 100.00%.

@@            Coverage Diff            @@
##            master      #264   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files            4         4           
  Lines          379       379           
=========================================
  Hits           379       379           

Impacted Files	Coverage Δ
pennylane_lightning/_version.py	100.00% <100.00%> (ø)

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[github-actions]

Test Report (C++) on Ubuntu

           1 files  ±0             1 suites  ±0   0s ⏱️ ±0s
       660 tests ±0         660 ✔️ ±0  0 💤 ±0  0 ❌ ±0 
228 174 runs  ±0  228 174 ✔️ ±0  0 💤 ±0  0 ❌ ±0 

Results for commit a27c8a4. ± Comparison against base commit 368b2bb.

♻️ This comment has been updated with latest results.

[mlxd]

Thanks @chaeyeunpark
Do the changes require an update to the CI to build and run the test-suite there also?

[chaeyeunpark]

Do the changes require an update to the CI to build and run the test-suite there also?

Hi @mlxd, not yet, but I am anyway planning to add tests on Windows with MSVC in CI for C++ code coverage (in a following PR).

[mlxd]

Do the changes require an update to the CI to build and run the test-suite there also?

Hi @mlxd, not yet, but I am anyway planning to add tests on Windows with MSVC in CI for C++ code coverage (in a following PR).

Great, thanks @chaeyeunpark
I'll approve when all tests are green.

[maliasadi]

Neat update @chaeyeunpark. Happy to approve.