perf: optimise `SyntaxNodeComparer` #211

Job	Run time
Run Tests	1m 17s
Check TODOs	8s
No Warnings	1m 0s
Check Formatting	16s
Test CSharpier.MSBuild (ubuntu-latest)	1m 37s
Test CSharpier.MSBuild (windows-latest)	2m 22s
Builds Playground	59s
	7m 39s

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