Make it possible to avoid the warning when replacing docstrings

[timholy]

The fact that doc! always warns led Revise to skip doc! calls but that led to a bug, timholy/Revise.jl#309. The fix in timholy/Revise.jl#310 basically requires copy-pasting the definition of doc!, which seems like a bad idea. This just adds an extra optional argument that allows one to suppress generation of the warning. Non-breaking but probably not advisable to backport since it's a new feature.

EDIT: alternatively this could be a keyword argument.

[KristofferC]

Shouldn't we do the same as we did for function replacements? That is, only warn if generating output?

[timholy]

Link please?

[KristofferC]

#23002

[timholy]

Fair to ask: can anyone give an example where that warning is clearly useful? #23011 (comment) says it can be useful but I am not sure about the circumstances.

This will help answer @KristofferC 's question, which I guess comes down to the issue of whether it's useful in any context other than module definition. Question: if these warnings are off by default except during precompilation, doesn't that suppress the warning for packages marked __precompile__(false)? (EDIT: answer is yes, the warnings don't show in that case.) Shouldn't we also show them if we are includeing a file?

[KristofferC]

Just as a note, feel free to ignore this whole tangent if you wish, just a thought I had with its relation to method overwrite warnings.