Add destructured context container to usedContexts

[jacobmischka]

Fixes #1139

I also rewrote a little chunk that had a variable that wasn't being used anywhere anymore.

[jacobmischka]

It's possible that this line could be removed in this circumstance, but I'm not sure enough to do so and it doesn't seem to hurt anything being there, ha.

31de60e#diff-faf6bf53ae607c055bf386d2fe896c01L256

Edit: Not removed I mean, just that we probably don't need to add the non-destructured name to contexts as well. Of course the name should still be added in other cases.

[codecov-io]

Codecov Report

Merging #1145 into master will decrease coverage by 0.04%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master    #1145      +/-   ##
==========================================
- Coverage   91.48%   91.44%   -0.05%     
==========================================
  Files         126      126              
  Lines        4521     4522       +1     
  Branches     1458     1459       +1     
==========================================
- Hits         4136     4135       -1     
  Misses        163      163              
- Partials      222      224       +2

Impacted Files	Coverage Δ
src/generators/Generator.ts	93.63% <100%> (-0.5%)	⬇️

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[Rich-Harris]

niiiice 👍