alias self-mutilation, self-injury -> self_harm

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BUR #17067 has been approved by @nonamethanks.

create alias self-mutilation -> self_harm
create alias self-injury -> self_harm

"Self-harm, self-injury, and self-mutilation are often used interchangeably" according to this source (PDF link). The wiki for self-mutilation is practically the same as self harm. self-injury will be a utility alias.