Add Class#inherits_method_missing

[st0012]

By default, method_missing's behavior is non-inheritable in Goby. So the following code will fail

class Foo
  def method_missing(name)
    10
  end
end

class Bar < Foo
end
		
Bar.new.bar #=> NoMethodError

But after this PR, you just need to call inherits_method_missing in the children class (Bar in the example) and then it can inherit method_missing from its ancestors

class Foo
  def method_missing(name)
    10
  end
end

class Bar < Foo
  inherits_method_missing
end
		
Bar.new.bar #=> 10

[codecov]

Codecov Report

Merging #676 into master will decrease coverage by 0.02%.
The diff coverage is 76.92%.

@@            Coverage Diff             @@
##           master     #676      +/-   ##
==========================================
- Coverage   81.86%   81.84%   -0.03%     
==========================================
  Files          57       57              
  Lines        7727     7749      +22     
==========================================
+ Hits         6326     6342      +16     
- Misses       1132     1136       +4     
- Partials      269      271       +2

Impacted Files	Coverage Δ
vm/object.go	83.01% <100%> (+1.01%)	⬆️
vm/instruction.go	92.6% <100%> (ø)	⬆️
vm/class.go	84.11% <68.42%> (-0.5%)	⬇️

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