Update queue size after the element is done exported

[bogdandrutu]

This PR changes when the size of the queues is updated, previously the size was updated when the element was removed from the queue but before was fully consumed (done callback was called), after this PR the size is updated when done callback is called.

This change ensures that the queue size limit applies to the whole exporter and allows better memory control for the users.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 91.55%. Comparing base (0831231) to head (63a413c).
Report is 4 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main   #12399   +/-   ##
=======================================
  Coverage   91.54%   91.55%           
=======================================
  Files         467      467           
  Lines       25623    25652   +29     
=======================================
+ Hits        23456    23485   +29     
  Misses       1768     1768           
  Partials      399      399           

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