The dev-mode warning wrapper on Array.includes induces a significant performance penalty on some hot paths in Svelte's internals. Eg. the slowest part in rendering this bar chart page (#17176 (comment)) in dev mode is the sources.includes in depends_on. This change gives me a roughly 4x improvement in rendering the bar chart page in dev.

This pr changes all usage of Array.includes in reactivity internals to use the un-wrapped index_of export instead. Only thing I'm not sure of is whether to use that index_of, or add a new re-export for array_includes.

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