ArraySeq instance follow-up

[travisbrown]

This builds on #3273, addressing #2994. It adds a few instances that were missing and makes the cats-kernel prioritization traits package-private.

[codecov-io]

Codecov Report

Merging #3302 into master will increase coverage by <.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master    #3302      +/-   ##
==========================================
+ Coverage   93.15%   93.15%   +<.01%     
==========================================
  Files         378      378              
  Lines        7579     7585       +6     
  Branches      203      204       +1     
==========================================
+ Hits         7060     7066       +6     
  Misses        519      519

Flag	Coverage Δ
#scala_version_212	93.38% <ø> (-0.02%)	⬇️
#scala_version_213	92.93% <100%> (+0.01%)	⬆️

Impacted Files	Coverage Δ
....13+/cats/kernel/instances/ArraySeqInstances.scala	100% <ø> (ø)	⬆️
...src/main/scala-2.13+/cats/instances/arraySeq.scala	100% <100%> (ø)	⬆️

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[kailuowang]

LGTM

[LukaJCB]

Doesn't have to be this PR, but we could add a TraverseFilter instance as well. :)
Happy to merge this as is though.

[travisbrown]

@LukaJCB @BalmungSan already got TraverseFilter in #3273! 😄