refactor(sync): get rid of RWMutex and TryLock

[tzdybal]

Overview

Checklist

• [ ] New and updated code has appropriate documentation
• [ ] New and updated code has new and/or updated testing
• [ ] Required CI checks are passing
• [ ] Visual proof for any user facing features like CLI or documentation updates
• [ ] Linked issues closed with keywords

[codecov-commenter]

Codecov Report

Merging #65 (ce00a07) into hlib/sync/new-net-head-race (a1322fc) will increase coverage by 0.06%. The diff coverage is 100.00%.

@@                       Coverage Diff                       @@
##           hlib/sync/new-net-head-race      #65      +/-   ##
===============================================================
+ Coverage                        65.60%   65.66%   +0.06%     
===============================================================
  Files                               35       35              
  Lines                             2832     2837       +5     
===============================================================
+ Hits                              1858     1863       +5     
  Misses                             817      817              
  Partials                           157      157              

Impacted Files	Coverage Δ
sync/sync.go	64.32% <100.00%> (ø)
sync/sync_getter.go	92.30% <100.00%> (+1.83%)	:arrow_up: