fix & feat: enhanced completion for zsh

[RocketMaDev]

I fixed zsh completion which is not working properly (like #549), now files can be completed. What's more, I add a feature that when triggering Tab where dependencies should be entered, the dependencies of the elf will pop out. Here's a screenshot:

If the elf is the first arg, it works, too:

In any other cases (file is not exist, or is a .so, or is not exist), the match fallback to the default _files match.

I tried my best to test all the cases on my machine and it should be right.

[RocketMaDev]

I've tested a lot and everything works. Would there be someone help me merge it in?