Denser output for duplicate dependency warnings

[djc]

Is your feature request related to a problem? Please describe.
Especially when getting started, it's hard to read the abundant output from cargo deny. I also find it confusing that there are 3 top-level warnings to describe one "problem".

warning: found 2 duplicate entries for crate 'nom'

    ┌── /Users/djc/src/valuex/Cargo.lock:83:1 ───
    │
 83 │ ╭ nom 4.2.3 registry+https://github.com/rust-lang/crates.io-index
 84 │ │ nom 5.1.0 registry+https://github.com/rust-lang/crates.io-index
    │ ╰───────────────────────────────────────────────────────────────^ lock entries
    │

warning: duplicate #1 (82) nom = 4.2.3

    ┌── /Users/djc/src/valuex/Cargo.lock:83:1 ───
    │
 83 │ nom 4.2.3 registry+https://github.com/rust-lang/crates.io-index
    │ ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ lock entry
    │
    = nom v4.2.3
      └── weedle v0.10.0
          └── wasm-bindgen-webidl v0.2.58
              └── (build) web-sys v0.3.35
                  └── ring v0.16.9
                      └── backend v0.1.0

warning: duplicate #2 (83) nom = 5.1.0

    ┌── /Users/djc/src/valuex/Cargo.lock:84:1 ───
    │
 84 │ nom 5.1.0 registry+https://github.com/rust-lang/crates.io-index
    │ ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ lock entry
    │
    = nom v5.1.0
      └── askama_derive v0.9.0
          └── askama v0.9.0
              └── backend v0.1.0

Describe the solution you'd like
A single warning would, I think, be easier to understand, along the lines of:

warning: found 2 duplicate entries for crate 'nom'

    ┌── /Users/djc/src/valuex/Cargo.lock:83:1 ───
    │
 83 │ ╭ nom 4.2.3 registry+https://github.com/rust-lang/crates.io-index
 84 │ │ nom 5.1.0 registry+https://github.com/rust-lang/crates.io-index
    │ ╰───────────────────────────────────────────────────────────────^ lock entries

    = nom v4.2.3
      └── weedle v0.10.0
          └── wasm-bindgen-webidl v0.2.58
              └── (build) web-sys v0.3.35
                  └── ring v0.16.9
                      └── backend v0.1.0

    = nom v5.1.0
      └── askama_derive v0.9.0
          └── askama v0.9.0
              └── backend v0.1.0

[Jake-Shadle]

I think this was mainly just a byproduct of how the inverted dependency trees are currently injected, I was planning on doing some cleanup around this today anyways.

[djc]

The new release is awesome! One tiny nit: I would probably still put an empty line between each of the dependency trees, currently they are kinda mashed together

warning: found 2 duplicate entries for crate 'generic-array'

    ┌── /Users/djc/src/valuex/Cargo.lock:47:1 ───
    │
 47 │ ╭ generic-array 0.12.3 registry+https://github.com/rust-lang/crates.io-index
 48 │ │ generic-array 0.13.2 registry+https://github.com/rust-lang/crates.io-index
    │ ╰──────────────────────────────────────────────────────────────────────────^ lock entries
    │
    = generic-array v0.12.3
      ├── block-buffer v0.7.3
      │   └── sha2 v0.8.1
      │       └── postgres-protocol v0.5.0
      │           ├── postgres-types v0.1.0
      │           │   └── tokio-postgres v0.5.1
      │           │       ├── backend v0.1.0
      │           │       └── bb8-postgres v0.4.0
      │           │           └── backend v0.1.0 (*)
      │           └── tokio-postgres v0.5.1 (*)
      ├── crypto-mac v0.7.0
      │   └── hmac v0.7.1
      │       └── postgres-protocol v0.5.0 (*)
      └── digest v0.8.1
          ├── hmac v0.7.1 (*)
          └── sha2 v0.8.1 (*)
    = generic-array v0.13.2 <-- insert empty line here ^^^?
      └── postgres-protocol v0.5.0
          ├── postgres-types v0.1.0
          │   └── tokio-postgres v0.5.1
          │       ├── backend v0.1.0
          │       └── bb8-postgres v0.4.0
          │           └── backend v0.1.0 (*)
          └── tokio-postgres v0.5.1 (*)