Added Cargo build-dir support to local command

[ranger-ross]

This PR adds basic build.build-dir as mentioned in #143

This implementation is not optimal as it relies on the internal structure of the Cargo target-dir and build-dir.
But the current functionality of cargo-cache needs to look into target and build dir.

The output of the command has been updated to take the build-dir into account.

Below are some samples of the new format.

---

build-dir not specified

cargo build 
cargo cache local

Project "/home/ross/projects/cargo-cache"

Target dir: /home/ross/projects/cargo-cache/target
    Total Size:       820.55 MB
    debug:            820.55 MB

---

With build-dir point to a local build directory

export CARGO_BUILD_BUILD_DIR=build
cargo +nightly -Zbuild-dir build
cargo +nightly -Zbuild-dir cache local

Project "/home/ross/projects/cargo-cache"

Target dir: /home/ross/projects/cargo-cache/target
    Total Size:       75.17 MB
    debug:            75.17 MB

Build dir: /home/ross/projects/cargo-cache/build
    Total Size:       731.98 MB
    debug:            731.97 MB

---

This PR is current blocked waiting on cargo_metadata to publish a release that includes oli-obk/cargo_metadata#297

cc: @epage @weihanglo
cc: rust-lang/cargo#14125