### What it does
Denies the configured macros in clippy.toml

Note: Even though this lint is warn-by-default, it will only trigger if
macros are defined in the clippy.toml file.

### Why is this bad?
Some macros are undesirable in certain contexts, and it's beneficial to
lint for them as needed.

### Example
An example clippy.toml configuration:
```
disallowed-macros = [
    # Can use a string as the path of the disallowed macro.
    "std::print",
    # Can also use an inline table with a `path` key.
    { path = "std::println" },
    # When using an inline table, can add a `reason` for why the macro
    # is disallowed.
    { path = "serde::Serialize", reason = "no serializing" },
]
```
```
use serde::Serialize;

// Example code where clippy issues a warning
println!("warns");

// The diagnostic will contain the message "no serializing"
#[derive(Serialize)]
struct Data {
    name: String,
    value: usize,
}
```