WIP: Implementing RStruct methods for `StableApiDefinition` in order to support TruffleRuby #901

Job	Run time
Bundle install in Dockerfile	57s
oxi-test (ruby=3.0, os=ubuntu-latest)	1m 18s
oxi-test (ruby=3.2, os=ubuntu-latest)	1m 20s
oxi-test (ruby=3.3, os=ubuntu-latest)	1m 0s
oxi-test (ruby=3.0, os=windows-latest)	5m 0s
oxi-test (ruby=3.2, os=windows-latest)	5m 0s
oxi-test (ruby=3.3, os=windows-latest)	5m 0s
oxi-test (ruby=3.0, os=macos-latest)	58s
oxi-test (ruby=3.2, os=macos-latest)	56s
oxi-test (ruby=3.3, os=macos-latest)	53s
magnus-0.5 (ruby=3.0, os=ubuntu-latest)	1m 30s
magnus-0.5 (ruby=3.2, os=ubuntu-latest)	1m 23s
magnus-0.5 (ruby=3.3, os=ubuntu-latest)	1m 12s
magnus-0.5 (ruby=3.0, os=windows-latest)	5m 2s
magnus-0.5 (ruby=3.2, os=windows-latest)	5m 3s
magnus-0.5 (ruby=3.3, os=windows-latest)	5m 1s
magnus-0.5 (ruby=3.0, os=macos-latest)	59s
magnus-0.5 (ruby=3.2, os=macos-latest)	1m 4s
magnus-0.5 (ruby=3.3, os=macos-latest)	1m 11s
magnus-head (ruby=3.0, os=ubuntu-latest)	2m 23s
magnus-head (ruby=3.2, os=ubuntu-latest)	2m 34s
magnus-head (ruby=3.3, os=ubuntu-latest)	2m 31s
magnus-head (ruby=3.0, os=windows-latest)	5m 3s
magnus-head (ruby=3.2, os=windows-latest)	5m 6s
magnus-head (ruby=3.3, os=windows-latest)	5m 8s
magnus-head (ruby=3.0, os=macos-latest)	1m 28s
magnus-head (ruby=3.2, os=macos-latest)	1m 26s
magnus-head (ruby=3.3, os=macos-latest)	1m 24s
	1h 11m 50s

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