feature request: add ability to enforce no blank lines in fn implementations

Currently there is an option to specify minimum and maximum of blank lines between items.

I think it would be nice if the option set would be expanded with:
maximum-blank-lines-in-fn-definitions.

I personally sometimes add blank lines for readability, but I can see the argument for not having any blank lines in the functions at all, ( and I do often end up landing blank lines at random )
it gives a coherent style across a codebase.

Example:
Instead of:

fn mini() {}

fn something(a: i32) -> i32 {
  if (a == 3) {
    return 0;
  }
  
  return 1;
}

A requested formatting would tighten up this code to:

fn mini() {} 

fn something(a: i32) -> i32 {
  if (a == 3) {
    return 0;
  }
  return 1;
}

Note that spacing between the defs would remain the same.
I think the defs of types should still allow a separation of inside the fn definitions. ( but that may be my prejudice speaking )

Start by tracing the existing minimum and maximum blank-line options in rustfmt and compare their behavior with the Rust examples in this issue. The change is complete when a maximum-blank-lines-in-fn-definitions option removes excess blank lines inside function bodies while preserving spacing between function definitions and allowing the stated type-definition behavior.