Add build-ids to drmodtrack library info

This was raised here: https://groups.google.com/g/dynamorio-users/c/iHL-m2sxDys/m/0pjziQ0KCQAJ?utm_medium=email&utm_source=footer

These days for Linux most packages are built with build-ids in all their binaries. These are useful for uniquely identifying modules. They can be added using drmodtrack's additional field interface (we are doing that today in drmemtrace usage), but the proposal here is to add them as a first-class field in drmodtrack.