Refactor: simplify and optimize `ElasticGraph::GraphQL::Schema`. #125

Job	Run time
ci-check (run_each_gem_spec, 3.2, elasticsearch:8.15.3)	16m 53s
ci-check (run_each_gem_spec, 3.2, opensearch:2.17.1)	16m 47s
ci-check (run_each_gem_spec, 3.2, opensearch:2.7.0)	16m 49s
ci-check (run_each_gem_spec, 3.3, elasticsearch:8.15.3)	17m 12s
ci-check (run_each_gem_spec, 3.3, opensearch:2.17.1)	15m 52s
ci-check (run_each_gem_spec, 3.3, opensearch:2.7.0)	16m 16s
ci-check (run_misc_checks, 3.3, elasticsearch:8.15.3)	8m 29s
ci-check (run_most_specs_with_vcr, 3.3, elasticsearch:8.15.3)	9m 20s
ci-check (run_specs_file_by_file, 3.3, elasticsearch:8.15.3)	14m 57s
All CI Checks Passed	1s
	2h 12m 36s

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