Optimize some predicate methods with attr_reader

[amomchilov]

When I was tinkering around and profiling GraphQL Ruby around a year ago, I found some small+easy perf wins from optimizing some commonly queried "predicate methods", by defining them via attr_reader. I've lost the benchmarks, and don't have time to recreate them, but I still figured it's worth sharing the idea here.

Unfortunately, Ruby makes these unnecessarily ugly/difficult in the case of boolean attributes, but still possible with this method swizzling dance:

attr_reader :foo         # Define the fast method with a temporary name
alias_method :foo?, :foo # Give it a nice name
remove_method :foo       # Delete the temporary name

The main cuplrits were in type_kind.rb. I've opened a PoC PR here: #5082

Candidates for this kind of replacement can be found with these 2 regexes:

def ([a-z0-9_]+)\??[;\n]\s*@\1[;\n]\s*end
def ([a-z0-9_]+)\??\s*=\s*@\1

(They can be merged into one, but I opted not to, just to keep them somewhat legible)

Would you be able to take a quick stab at benchmarking these? And in general, do you think those perf wins are worth this ugliness?