Reduce impact of native samples on Gradle distribution size

It looks like the majority of the `-src` Gradle distribution's size is due to native samples. We should investigate if there's something easy we can do to. This also affects the `-all` distribution.

We'll make a particular Frenchman happy.

Start by investigating how native samples are included in the `-src` and `-all` Gradle distributions. Compare their contents and size, then determine whether they can be reduced without losing needed samples; done means a smaller distribution with native sample coverage preserved.

Written by the indexing model from the issue text.