Make `comment_references` fixes add doc imports instead of normal imports

[FMorschel]

After #59723, inspired by #59741 and #59724. I'm opening this issue to track the work for making the fixes for comment_references (edited in #59723) into fixes that add doc imports and not normal imports.

//CC @srawlins and @bwilkerson

[FMorschel]

There is also no reference to doc imports on the docs for comment_references (see https://dart.dev/tools/linter-rules/comment_references). So this should probably address this too.