CI Updates and removal of POMDPSimulators from tests

[dylan-asmar]

Updated the CI to run tests and publish the coverage. The last update on codecov was commit 269f495 (~4 years ago).

Updated .gitignore to include Manifest.toml and .vscode for vscode users.

Removed POMDPSimulators from the tests since it uses POMDPTools now.

[codecov]

Codecov Report

Attention: 3 lines in your changes are missing coverage. Please review.

Comparison is base (269f495) 47.11% compared to head (1813ead) 87.27%.
Report is 41 commits behind head on master.

Files	Patch %	Lines
src/memorizing_rng.jl	87.50%	2 Missing ⚠️
src/pomdps_glue.jl	75.00%	1 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           master      #33       +/-   ##
===========================================
+ Coverage   47.11%   87.27%   +40.16%     
===========================================
  Files          12       12               
  Lines         433      511       +78     
===========================================
+ Hits          204      446      +242     
+ Misses        229       65      -164     

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