maps: make sure AuthorMaps don't overwrite themselves, fix overriding Author maps for the Python repo got truncated because of the author map stupidly writing upon itself. This patch implements a better and faster scenario, where entries will only be written to the saved author map if they're not coming from that file. They're also now streamed into the file directly, instead of having to re-open the file on every entry, and formatting is preserved.

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