Make `runDepmod` behave more like `build-image-kernel-modules`

modules.load defaults to filenames of the .ko files listed in `srcs`.
This CL adds a property to skip this behvaior, thereby creating an empty
modules.load file. This will be used to build system_dlkm.img of some
products whose `BOARD_SYSTEM_KERNEL_MODULES_LOAD` is empty.

Bug: 377562851
Test: verified that /system_dlkm/lib/modules/modules.dep is empty for
both kati and soong for aosp cf
Test: verified that modules.* files are not created for odm_dlkm.img
built with soong (top of CL stack)

Change-Id: I8a0304fda1b5cc2ea0d1f36334877beca26f1d8a