Display all Cargo target executables in `cargo metadata` or similar command

[bruno-medeiros]

Enhancement: a command to display all Cargo targets (including implicit test targets such as bin-tests and lib-tests) and their associated executable.

See also: #1924

[alexcrichton]

cc @matklad

[matklad]

Enhancement: a command to display all Cargo targets

cargo metadata already does this.

and their associated executable.

There can be several executables for one target (target/debug/foo, target/release/foo).

[matklad]

I just realized that currently the test binary for #[test] tests aren't included in cargo read-manifest output.

Ah, yes, now I also realize this.