search path functionality should be smarter and faster

[sdimitro]

The -s option can be slow when ran against fully copied /lib/module and /usr/lib/debug/lib/module` paths that contain many unnecessary modules for the target dump that is being examined. Besides being slow, it's naive algorithm is also prone to issues like running out of open file handles (see #202).

We should change its behavior so that once the appropriate vmlinux has been loaded up, sdb goes through list of modules that were loaded when the crash dump was captured, and only look for the .ko files that match them.

Fixing this bug will involve creating an extra step on SDB's initialization of the underlying DRGN session and getting rid of the naive algorithm.