Change the definition of `tagtype` from `functype` into `deftype` #269

Job	Run time
build-js-api-spec	26s
build-legacy-exceptions-core-spec	1m 45s
build-core-spec	8m 18s
build-legacy-exceptions-js-api-spec	29s
build-spec-versions	6s
build-web-api-spec	28s
build-code-metadata-spec	2m 57s
publish-spec	16s
	14m 45s

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