Cleanup the operator classes package layout

[jponge]

No description provided.

[jponge]

@cescoffier here's a reworked layout, but it fails right now due to RevApi.

[codecov]

Codecov Report

Merging #452 (f624a2b) into master (d41996d) will increase coverage by 0.00%.
The diff coverage is n/a.

@@            Coverage Diff            @@
##             master     #452   +/-   ##
=========================================
  Coverage     90.15%   90.16%           
+ Complexity     2871     2870    -1     
=========================================
  Files           373      373           
  Lines         10952    10952           
  Branches       1344     1346    +2     
=========================================
+ Hits           9874     9875    +1     
  Misses          547      547           
+ Partials        531      530    -1     

Impacted Files	Coverage Δ	Complexity Δ
...java/io/smallrye/mutiny/groups/MultiBroadcast.java	100.00% <ø> (ø)	5.00 <0.00> (ø)
...n/java/io/smallrye/mutiny/groups/MultiIfEmpty.java	100.00% <ø> (ø)	20.00 <0.00> (ø)
...o/smallrye/mutiny/groups/MultiItemCombination.java	100.00% <ø> (ø)	10.00 <0.00> (ø)
...a/io/smallrye/mutiny/groups/MultiItemCombine2.java	100.00% <ø> (ø)	6.00 <0.00> (?)
...a/io/smallrye/mutiny/groups/MultiItemCombine3.java	100.00% <ø> (ø)	6.00 <0.00> (?)
...a/io/smallrye/mutiny/groups/MultiItemCombine4.java	100.00% <ø> (ø)	6.00 <0.00> (?)
...a/io/smallrye/mutiny/groups/MultiItemCombine5.java	83.33% <ø> (ø)	5.00 <0.00> (?)
...a/io/smallrye/mutiny/groups/MultiItemCombine6.java	84.61% <ø> (ø)	5.00 <0.00> (?)
...a/io/smallrye/mutiny/groups/MultiItemCombine7.java	84.61% <ø> (ø)	5.00 <0.00> (?)
...a/io/smallrye/mutiny/groups/MultiItemCombine8.java	84.61% <ø> (ø)	5.00 <0.00> (?)
... and 70 more

[jponge]

I ended up adding the RevApi documentation for the changes. I did my best to dispatch classes where I think they'd make sense, but please look carefully 😉