Change the AssertSubscriber items list back to copyOnWrite

[ozangunalp]

This changes the AssertSubscriber items list back tyo CopyOnWriteArrayList.

The synchronized list is not very practical to write assertions with concurrent access to the list. It requires that the list access is also synchronized on the list.

[jponge]

Ok to merge, but you'll need to fix the commit message to something like:

fix: change the AssertSubscriber items list back to CopyOnWriteArrayList

[jponge]

Do you need a fast-tracked patch release for Reactive Messaging?

[codecov]

Codecov Report

Merging #1386 (3ec4341) into main (477b3fc) will increase coverage by 0.05%.
Report is 1 commits behind head on main.
The diff coverage is 100.00%.

❗ Current head 3ec4341 differs from pull request most recent head 5442f2c. Consider uploading reports for the commit 5442f2c to get more accurate results

Additional details and impacted files

@@             Coverage Diff              @@
##               main    #1386      +/-   ##
============================================
+ Coverage     89.19%   89.24%   +0.05%     
- Complexity     3361     3364       +3     
============================================
  Files           459      459              
  Lines         13438    13438              
  Branches       1655     1655              
============================================
+ Hits          11986    11993       +7     
+ Misses          806      803       -3     
+ Partials        646      642       -4     

Files	Coverage Δ
...smallrye/mutiny/helpers/test/AssertSubscriber.java	91.91% <100.00%> (ø)

... and 9 files with indirect coverage changes