Optimize sync iterator

[Adda0]

This PR slightly optimizes SynchronizedIterator and its uses.

[codecov]

Codecov Report

Attention: 1 lines in your changes are missing coverage. Please review.

Comparison is base (b288936) 71.68% compared to head (b7bc4a0) 71.68%.
Report is 1 commits behind head on devel.

Additional details and impacted files

@@           Coverage Diff           @@
##            devel     #361   +/-   ##
=======================================
  Coverage   71.68%   71.68%           
=======================================
  Files          30       30           
  Lines        3617     3617           
  Branches      830      830           
=======================================
  Hits         2593     2593           
  Misses        735      735           
  Partials      289      289           

Files	Coverage Δ
include/mata/utils/synchronized-iterator.hh	82.02% <100.00%> (ø)
src/nfa/intersection.cc	79.41% <100.00%> (ø)
src/nfa/operations.cc	64.33% <100.00%> (ø)
src/nfa/delta.cc	82.74% <50.00%> (ø)

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