Eliminate type parameters from abstract types and add fullbasis function

[akirakyle]

Following on discussion in #26 and #34, this is the first step towards improving the api around basis, by eliminating the type parameters from the abstract quantum object types and adding fullbasis. This will require minimal changes to QuantumOpticsBase because the currently necessary type parameters can be reintroduced when subtyping the abstract types.

PS, this PR is already on top of #37.

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 72 lines in your changes missing coverage. Please review.

Project coverage is 34.25%. Comparing base (f22adb7) to head (3fc123c).

Files with missing lines	Patch %	Lines
src/show.jl	0.00%	43 Missing ⚠️
src/julia_base.jl	0.00%	15 Missing ⚠️
src/linalg.jl	0.00%	5 Missing ⚠️
src/bases.jl	0.00%	3 Missing ⚠️
src/embed_permute.jl	0.00%	3 Missing ⚠️
src/julia_linalg.jl	0.00%	2 Missing ⚠️
src/identityoperator.jl	0.00%	1 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##             main      #38       +/-   ##
===========================================
+ Coverage   17.08%   34.25%   +17.16%     
===========================================
  Files          12       12               
  Lines         398      400        +2     
===========================================
+ Hits           68      137       +69     
+ Misses        330      263       -67     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[Krastanov]

Thanks! I will try to find some time to look into this work.

A minor nit: if you are moving around a lot of code without modifying it, it helps a lot to have the moving and the editing in separate commits -- the review is much faster as the reviewer has an easier time focusing on the actual edits without wasting time on verifying that code is simply moved. No need to do it here after the fact, just a heads up for next time.

[akirakyle]

The reorganization is the first commit here, which is also alone in PR in #37, since I figured you would see that first after the review request, then I would request review here only after that had been merged. If this is too confusing, let me know whatever is easiest for you! I admit I'm not so adept at the github interface since I usually use magit in emacs 😅

[akirakyle]

Converting to a draft for now since I just realized methods in expect_variance.jl assume type parameters to AbstractOperator to check if the bases are equal and so is broken by removing the type parameters. That means removing type parameters will have to wait on resolving the interface in #34 for how we want to handle compatible basis checks.

[akirakyle]

Closing in favor of #42