Replace pop with indexing in reshape_samples

[thisac]

Context:
The reshape_samples function in tdmprogram.py currently works by popping elements from the all_samples dictionary that's being sent in as an argument, and then inserting them into a new dictionary which is then returned. This causes the sent in all_samples dictionary to be empty after having reshaped the samples (which might be confusing for the user, since this is nowhere stated).

This is not really an optimal way of handling things, and should probably be fixed.

Description of the Change:
The popping of samples from the input all_samples dictionary is changed to indexing, while keeping track of used indices. Thanks to @lneuhaus for pointing this out!

Benefits:
This method doesn't change the input all_samples and it should be equally fast as before, if not faster.

Possible Drawbacks:
None

Related GitHub Issues:
None

[codecov]

Codecov Report

Merging #548 (8fb32dc) into master (9ee646f) will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master     #548   +/-   ##
=======================================
  Coverage   98.19%   98.19%           
=======================================
  Files          76       76           
  Lines        8327     8329    +2     
=======================================
+ Hits         8177     8179    +2     
  Misses        150      150           

Impacted Files	Coverage Δ
strawberryfields/tdm/tdmprogram.py	95.72% <100.00%> (+0.04%)	⬆️

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[lneuhaus]

Great! Nothing to add here.