rx (feature): Support join/zip upto 5 elements

[xerial]

Fixes #3079

[codecov]

Codecov Report

Merging #3089 (facc74a) into master (5a51958) will increase coverage by 0.00%.
The diff coverage is 94.73%.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #3089   +/-   ##
=======================================
  Coverage   82.85%   82.86%           
=======================================
  Files         349      349           
  Lines       14681    14689    +8     
  Branches     2487     2493    +6     
=======================================
+ Hits        12164    12172    +8     
  Misses       2517     2517           

Files Changed	Coverage Δ
...rx/src/main/scala/wvlet/airframe/rx/RxRunner.scala	91.85% <75.00%> (+0.08%)	⬆️
...frame-rx/src/main/scala/wvlet/airframe/rx/Rx.scala	82.10% <100.00%> (+1.20%)	⬆️

... and 1 file with indirect coverage changes

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