Improve "unknown field" error messages

Fixes rust-lang#8806

Sample output:
```
error: error reading Clippy's configuration file `/home/smoelius/github/smoelius/rust-clippy/clippy.toml`: unknown field `foobar`, expected one of
           allow-expect-in-tests              enable-raw-pointer-heuristic-for-send    standard-macro-braces
           allow-unwrap-in-tests              enforced-import-renames                  third-party
           allowed-scripts                    enum-variant-name-threshold              too-large-for-stack
           array-size-threshold               enum-variant-size-threshold              too-many-arguments-threshold
           avoid-breaking-exported-api        literal-representation-threshold         too-many-lines-threshold
           await-holding-invalid-types        max-fn-params-bools                      trivial-copy-size-limit
           blacklisted-names                  max-include-file-size                    type-complexity-threshold
           cargo-ignore-publish               max-struct-bools                         unreadable-literal-lint-fractions
           cognitive-complexity-threshold     max-suggested-slice-pattern-length       upper-case-acronyms-aggressive
           cyclomatic-complexity-threshold    max-trait-bounds                         vec-box-size-threshold
           disallowed-methods                 msrv                                     verbose-bit-mask-threshold
           disallowed-types                   pass-by-value-size-limit                 warn-on-all-wildcard-imports
           doc-valid-idents                   single-char-binding-names-threshold
       at line 1 column 1
```

You can test this by (say) adding `foobar = 42` to Clippy's root `clippy.toml` file, and running `cargo run --bin cargo-clippy`.

Note that, to get the terminal width, this PR adds `termize` as a dependency to `cargo-clippy`. However, `termize` is also [how `rustc_errors` gets the terminal width](https://github.com/rust-lang/rust/blob/481db40311cdd241ae4d33f34f2f75732e44d8e8/compiler/rustc_errors/src/emitter.rs#L1607). So, hopefully, this is not a dealbreaker.

r? `@xFrednet`

changelog: Enhancements: the "unknown field" error messages for config files now wraps the field names.