message: [doc] Updates docs to remove workarounds for feature de-unification
  Closes:
  Approved by: rexhoffman
diff: @@ -300,9 +300,8 @@ conditions to perform this conditional compilation:
  as the conditional test-only code.
  - the `fuzzing` custom feature, which is used to enable fuzzing and testing
  related code in downstream crates. Note that this must be passed explicitly to
  -`cargo xtest` and `cargo x bench`. Never use this in `[dependencies]` or
  -`[dev-dependencies]` unless the crate is only for testing, otherwise Cargo's
  -feature unification may pollute production code with the extra testing/fuzzing code.
  +`cargo xtest` and `cargo x bench`. Never use this in `[dependencies]` unless
  +the crate is only for testing.
  As a consequence, it is recommended that you set up your test-only code in the following fashion.
  @@ -336,24 +335,12 @@ For the sake of example, we'll consider you are defining a test-only helper func
  default = []
  fuzzing = ["foo_crate/fuzzing"]
  ```
  -5. Update `x.toml` to run the unit tests passing in the features if needed.
  -
  -**Special case:** If a test-only crate (see below) is a dev-dependency of a production crate listed in the root
  -`Cargo.toml`'s `default-members`, it needs to be marked optional for feature resolution to work properly. Do this by
  -marking the dependency as optional and moving it to the `[dependencies]` section.
  -
  -```toml
  -[dependencies]
  -foo_crate = { path = "...", optional = true }
  -```
  -
  -(This is a temporary workaround for a Cargo issue and is expected to be addressed with Cargo's [new feature
  -resolver](https://github.com/rust-lang/cargo/pull/7820)).
  **For test-only crates:**
  Test-only crates do not create published artifacts. They consist of tests, benchmarks or other code that verifies
  -the correctness or performance of published artifacts. Test-only crates are explicitly listed in `x.toml`.
  +the correctness or performance of published artifacts. Test-only crates are
  +explicitly listed in `x.toml` under `[workspace.test-only]`.
  These crates do not need to use the above setup. Instead, they can enable the `fuzzing` feature in production crates
  directly.
  