info: add Binaries section listing executables

List the formula's bin/ and sbin/ executables in a new `==> Binaries`
section before `==> Caveats`. For installed formulae the list is read
from the linked keg; for not-installed formulae `--fetch-manifest`
triggers a fallback that reads from the bottle manifest, mirroring
how `Bottle Size` and `Installed Size` already behave.