perf: optimise `SyntaxNodeComparer` #246

Job	Run time
Run Tests	1m 14s
No Warnings	57s
Check Formatting	20s
Builds Playground	1m 1s
Test CSharpier.MSBuild (windows-latest)	2m 12s
Check TODOs	8s
Test CSharpier.MSBuild (ubuntu-latest)	1m 29s
	7m 21s

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