This patch updates all usage of toPlist such that it escapes any strings
in the final output.
The motication for this change is to avoid confusion when end-users of
home-manager's APIs are not aware that the option values they set end up
being passed un-escaped to XML files.
BREAKING CHANGE: Consumers doing manual escaping will now be doubly escaped.
Co-authored-by: Linnnus <linnnus@users.noreply.github.com>
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