Drop support of symbol hash keys

[imrefoldeskaligo]

Summary

Handling dynamic conversion between String and Symbol keys creates a significant perfomance bottleneck. With this change, if data is passed as Hash, keys need to be provided as String. As a result, we can expect ~30% performance improvement.

Test Suite

require 'benchmark/ips'
require "bundler/gem_tasks"
require 'json_logic'


data = { 'a' => 1, 'b' => { 'c' => 2, 'd' => 3 } }
logic = { 'var' => 'b.c' }

compiled = JSONLogic.compile(logic)

Benchmark.ips do |x|
  x.report("apply-compiled-logic") { compiled.evaluate(data) }
  x.compare!
end

Before PR

Warming up --------------------------------------
apply-compiled-logic    59.924k i/100ms
Calculating -------------------------------------
apply-compiled-logic    603.481k (± 1.4%) i/s -      3.056M in   5.065220s

After PR

Warming up --------------------------------------
apply-compiled-logic    79.318k i/100ms
Calculating -------------------------------------
apply-compiled-logic    799.975k (± 2.5%) i/s -      4.045M in   5.059387s