Fix/registry member destruction order

[DNKpp]

As discussed on discord, I would like to see the context variables get destructed after the component pools. This comes in handy, when a component tears down itself from a context var during destruction. As entt currently doesn't follow a intentional order, I suggest this one to be followed.

[codecov-commenter]

Codecov Report

Merging #930 (c00434f) into wip (eedecc0) will not change coverage. The diff coverage is 100.00%.

@@           Coverage Diff           @@
##              wip     #930   +/-   ##
=======================================
  Coverage   99.99%   99.99%           
=======================================
  Files         139      139           
  Lines       20833    20843   +10     
=======================================
+ Hits        20832    20842   +10     
  Misses          1        1           

Impacted Files	Coverage Δ
src/entt/entity/registry.hpp	100.00% <ø> (ø)
test/entt/entity/registry.cpp	100.00% <100.00%> (ø)

Help us with your feedback. Take ten seconds to tell us how you rate us. Have a feature suggestion? Share it here.

[skypjack]

Merging on a temporary branch to review a little the test and make it closer to the style of the rest of the library. 🙂