Create test for internal anchors in uppercase

What does this MR do?

Test internal documentation links to ensure their fragments (the portion after a #) are in lower case.

Uses the regex \[.+\]\((https?:){0}[\w\/\.-]+\.md#[a-z]*[A-Z].*?\) which I THINK gets us most of what we need, but the [a-z] may need more character sequences allowed, such as 0-9 and oddities like _-. I may also be overthinking this.

cc @katrinleinweber

Related issues

• Closes #227458 (closed)

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