[C++][Compute] Enhance FunctionOptions with equality, debug representability, and serializability

[asfimport]

Currently the FunctionOptions interface is entirely opaque. It would be useful to add

• equality comparability ```Java

  bool FunctionOptions::Equals(const FunctionOptions& other) const
  

• debug representation ```Java

  std::string FunctionOptions::ToString() const
  

• serializability ```Java

  Status FunctionOptions::Serialize(io::OutputStream*) const
  
  Result<std::unique_ptr<FunctionOptions>>
      FunctionOptions::Deserialize(io::InputStream*)
  

  
  These are already implemented for common instances of `FunctionOptions` in expression.cc, since `Expression` has the above capabilities and may contain a `FunctionOptions`. Making these explicit virtual functions will formalize this ad-hoc
  code and expose it for direct unit testing.
  
  As an added bonus, if options can serialize themselves to JSON then that can be used by Python and other bindings to generate wrappers instead of the current hand-written listing of wrapper classes for each `FunctionOptions` subclass
  
  

Reporter: Ben Kietzman / @bkietz
Assignee: David Li / @lidavidm

Related issues:

• [C++] C++ array kernels framework and execution buildout (umbrella issue) (is a child of)

PRs and other links:

• GitHub Pull Request #10511

_{Note: This issue was originally created as ARROW-13025. Please see the migration documentation for further details.}

[asfimport]

Antoine Pitrou / @pitrou:
+1 for the additional methods. I'm skeptical about JSON serialization, though.

[asfimport]

Ben Kietzman / @bkietz:
Issue resolved by pull request 10511
#10511