Feature request: Option to have one "use" statement per file

Currently imports_granularity = 'One' merges all imports into one "use" statement. In my opinion, functionally it does two separate things: 1) Combine all "use" statements; 2) apply imports_granularity = 'Crate' inside the braces. Obviously it has the advantage of having no duplicate "use". However, I also really like the style of imports_granularity = 'Module'. It's visually much clearer, and easier to modify one import without affecting other imports. Ideally, I'd love to see a style where it can combine the "one" use statement with the module style. For example,

use {
    foo::b::{f, g},
    foo::d::e,
    foo::{a, b, c},
    qux::{h, i},
};

I think imports_granularity is orthogonal to this one "use" statement style, so why not introduce a separate option like one_use_statement? With this new option, we will have 6 combinations in total:

1. imports_granularity = 'Crate' + one_use_statement = false

2. imports_granularity = 'Module' + one_use_statement = false

3. imports_granularity = 'Item' + one_use_statement = false
   These 3 will be exactly the same as current

4. imports_granularity = 'Crate' + one_use_statement = true
   This is basically identical to the current imports_granularity = 'One'

5. imports_granularity = 'Module' + one_use_statement = true
   The example is shown above

6. imports_granularity = 'Item' + one_use_statement = true

use {
    foo::a,
    foo::b,
    foo::b::f,
    foo::b::g,
    foo::c,
    foo::d::e,
    qux::h,
    qux::i,
};

With this new option, imports_granularity = 'One' is no longer needed.

The issue does not name files, tests, or an entry point. Start by locating rustfmt's existing imports_granularity configuration and related import-formatting tests, then determine how a separate one-use-statement option should interact with the existing modes and update coverage for the proposed combinations.