feat(cargo-acap-*): Add --manifest-path

[apljungquist]

Previously this could be passed to cargo after --, but doing so typically would not work since cargo-acap-build internally invokes Cargo to get the target dir. Now we explicitly parse that option and propagate it to all cargo subcommands.

I also considered leaving it after --, infer any manifest path from those args and propagate it explicitly only for the internal cargo sub- commands. I'm honestly unsure which is better.

Pros (of the current implementation):

• No fragile, ad-hoc parsing of arguments. There are many ways this could go wrong. We could forget to handle both "=" and " ", we could forget to handle "--" (any --manifest-path after such an argument would probably not go to cargo).
• It's clear to educated users which arguments directly affect the behavior of the cargo-acap-* programs.

Cons:

• The public interface of the programs change
• Our interface requires --manifest-path to come before the command while cargo expects it after the command.