Mark Ops traits as Serializable

[travisbrown]

The Ops traits generated by Simulacrum have never been marked Serializable, which can cause problems on Spark. We could make this an option but right now that seems like unnecessary complexity.

The important part here is adding Serializable to the Ops traits. I've also done the ToXOps ones for consistency, but I'm hoping we can deprecate them soon anyway.

[codecov-commenter]

Codecov Report

Merging #29 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master      #29   +/-   ##
=======================================
  Coverage   79.76%   79.76%           
=======================================
  Files           9        9           
  Lines         336      336           
  Branches        6        6           
=======================================
  Hits          268      268           
  Misses         68       68           

Impacted Files	Coverage Δ
...rg/typelevel/simulacrum/fix/TypeClassSupport.scala	90.22% <ø> (ø)

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