Add adaptive median filter

There is a version in [`RealAdaptiveMedianFunction`](https://github.com/imagej/imagej-deprecated/blob/master/src/main/java/net/imglib2/ops/function/real/RealAdaptiveMedianFunction.java) which currently lives in `imagej-deprecated` that should be used as a basis for the "new" op.

There's also a `Command` that could be refactored to use the new op: [`NoiseReductionAdaptiveMedian`](https://github.com/imagej/imagej-plugins-commands/blob/master/src/main/java/net/imagej/plugins/commands/assign/noisereduce/NoiseReductionAdaptiveMedian.java).

Start by reading RealAdaptiveMedianFunction.java in imagej-deprecated to understand the existing adaptive median implementation, then inspect NoiseReductionAdaptiveMedian.java in imagej-plugins-commands. Create the corresponding new op and refactor the command to use it; done means the command performs adaptive median noise reduction through the new op.

Written by the indexing model from the issue text.