Implement equivalent numpy median and quantile / percentile

[ricardoV94]

Please describe the purpose of filing this issue

Equivalent symbolic methods to those are missing.

The Numpy quantile and percentile methods have too many options for the interpolation argument, and these are planned to be deprecated for a while now (see https://github.com/numpy/numpy/issues/10736). It should suffice to implement the default "linear" interpolation.

I am confident that these should not require any extra Ops.