build: prune Boost headers in depends

The Boost 1.81.0 tarball is ~118mb, and expands to much larger than that, however we end up with ~150mb of headers copied into the /include/boost dir in depends. This is a lot by itself, and even more when it's 170mb * 9 (HOSTS for a guix build).

With the changes in this PR, we end up with ~50mb of Boost headers in depends, which with some creative patching/pruning, could be trimmed even further. i.e sometimes you end up pulling in an entire boost module, because of a single include in another header we use, but in code that we don't actually need. In other cases there are deprecated headers which are still being used, which could be removed if the modules we care about stopped using them. I will open some PRs upstream to try and improve that situation, ie: https://github.com/boostorg/multi_index/pull/57.