perf: net_dropmonitor: Use bisection in symbol lookup

def get_sym(sloc):

	loc = int(sloc)

	for symloc, name in kallsyms[::-1]:

		if loc >= symloc:

	# Invariant: kallsyms[i][0] <= loc for all 0 <= i <= start

	#            kallsyms[i][0] > loc for all end <= i < len(kallsyms)

	start, end = -1, len(kallsyms)

	while end != start + 1:

		pivot = (start + end) // 2

		if loc < kallsyms[pivot][0]:

			end = pivot

		else:

			start = pivot

	# Now (start == -1 or kallsyms[start][0] <= loc)

	# and (start == len(kallsyms) - 1 or loc < kallsyms[start + 1][0])

	if start >= 0:

		symloc, name = kallsyms[start]

		return (name, loc - symloc)

	else:

		return (None, 0)

def print_drop_table():