Add more module dirs to kldload

[Dystopian]

Current completion only shows modules from /boot/kernel/. There are more directories with modules now in FreeBSD e.g. local modules go usually to /boot/modules/. Looks like all current directories are written in sysctl variable kern.module_path (see also kldconfig(8)). New implementation considers all these paths.

I'm not experienced in bash programming so there can be some bugs. Tested on FreeBSD 12.3.

[scop]

Thanks! Some comments follow.

[Dystopian]

should we fall back to the previous hardcoded dirs if the utility we choose to use here yields nothing?

Due to man kldload(8) won't load anything if kldconfig -r is empty. I think no sense to use old hardcoded dirs as fallback.

Directory handling is added too so I thinks it's done.

[scop]

We have some more elaborate checks for what looks like a path in the tree, will convert this to use it after the merge.