Fix a concatMap race condition on inner and outer completions signals

[jponge]

No description provided.

[jponge]

Doesn't work so far

[codecov]

Codecov Report

Merging #1463 (e179924) into main (efba606) will increase coverage by 0.23%.
Report is 1 commits behind head on main.
The diff coverage is 83.33%.

Additional details and impacted files

@@             Coverage Diff              @@
##               main    #1463      +/-   ##
============================================
+ Coverage     89.12%   89.35%   +0.23%     
- Complexity     3351     3366      +15     
============================================
  Files           459      459              
  Lines         13402    13401       -1     
  Branches       1641     1641              
============================================
+ Hits          11944    11975      +31     
+ Misses          822      795      -27     
+ Partials        636      631       -5     

Files	Coverage Δ
...llrye/mutiny/operators/multi/MultiConcatMapOp.java	85.03% <83.33%> (-0.12%)	⬇️

... and 10 files with indirect coverage changes

[jponge]

@ozangunalp You might want to test this on RM 😉

[ozangunalp]

@jponge you might want to take a break :)