tree-sitter: further improve parsing of nested comments, extend tests #173

Job	Run time
build (ubuntu-20.04, debug)	27s
build (ubuntu-20.04, dev)	39s
build (ubuntu-20.04, release)	1m 24s
build (macos-latest, debug)	1m 8s
build (macos-latest, dev)	1m 14s
build (macos-latest, release)	2m 43s
build (windows-latest, debug)	2m 4s
build (windows-latest, dev)	1m 59s
build (windows-latest, release)	2m 39s
	14m 17s

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