Invert the quotes to fix code quality json, make messages active

What does this MR do?

As one step on the way towards enabling code quality for docs, we need to invert the quoting in the vale rules. The JSON is generating with double quotes around the message strings, so if there are double quotes inside the messages, it breaks the JSON. Changing to single quotes in messages, and double quotes outside the strings, seems to do the trick.

This is also a good opportunity for the docs team to review all the vale rule messages. We should make sure we're happy with the language before rolling them out to a more public view in MR diffs. These messages will be seen by all docs contributors, including first time contributors, so we should ensure the language makes the needed improvements clear to everyone.

Finally, it sets the code quality warning levels, to blocker (vale errors), warning (vale warnings), and info (vale suggestions), as per this screenshot:

Related issues

Related to #378718 (closed)

Author's checklist

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Reviewer's checklist

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