Use rb_sym2str instead of SYM2ID #228

Job	Run time
ruby-versions / Generate Ruby versions	1s
ubuntu-20.04 2.3	56s
ubuntu-20.04 2.4	53s
ubuntu-20.04 2.5	59s
ubuntu-20.04 2.6	59s
ubuntu-20.04 2.7	55s
ubuntu-20.04 3.0	21s
ubuntu-20.04 3.1	24s
ubuntu-20.04 3.2	21s
ubuntu-20.04 head	24s
ubuntu-20.04 jruby	1m 9s
ubuntu-20.04 jruby-head	1m 9s
ubuntu-22.04 2.3	53s
ubuntu-22.04 2.4	52s
ubuntu-22.04 2.5	59s
ubuntu-22.04 2.6	59s
ubuntu-22.04 2.7	2m 10s
ubuntu-22.04 3.0	22s
ubuntu-22.04 3.1	24s
ubuntu-22.04 3.2	22s
ubuntu-22.04 head	21s
ubuntu-22.04 jruby	1m 9s
ubuntu-22.04 jruby-head	1m 9s
macos-11 2.3	2m 11s
macos-11 2.4	2m 3s
macos-11 2.5	2m 0s
macos-11 2.6	2m 1s
macos-11 2.7	2m 3s
macos-11 3.0	37s
macos-11 3.1	38s
macos-11 3.2	35s
macos-11 head	37s
macos-11 jruby	1m 16s
macos-11 jruby-head	1m 22s
macos-12 2.3	2m 31s
macos-12 2.4	1m 58s
macos-12 2.5	2m 27s
macos-12 2.6	2m 5s
macos-12 2.7	2m 21s
macos-12 3.0	38s
macos-12 3.1	27s
macos-12 3.2	48s
macos-12 head	37s
macos-12 jruby	1m 55s
macos-12 jruby-head	2m 19s
windows-latest 2.3	1m 53s
windows-latest 2.4	2m 32s
windows-latest 2.5	3m 15s
windows-latest 2.6	4m 45s
windows-latest 2.7	2m 31s
windows-latest 3.0	1m 27s
windows-latest 3.1	1m 19s
windows-latest 3.2	1m 36s
windows-latest head	1m 54s
windows-latest mswin	2m 9s
ubuntu-latest jruby-9.1	1m 12s
ubuntu-latest jruby-9.2	1m 24s
ubuntu-latest jruby-9.3	1m 36s
macos-latest truffleruby	1m 38s
ubuntu-latest truffleruby	50s
	1h 21m 41s

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