Overflow flag when result is larget finite value

IeeeFloat::overflow_result ( in src/ieee.rs) returns Status::INEXACT alone on the finite-result path.
IEEE 754-2019 7.4 requires the overflow whenever the largest finite number is exceeded in magnitude by what would have been the rounded floating point result with an unbounded exponent range.
Whether the default result subsequently produced by the selected rounding mode is infinity or the largest finite value does not change whether overflow occurred.

In particular, the specification details overflow for roundTowardZero and roundTowardNegative even with a non inf result.

use rustc_apfloat::ieee::Quad;
use rustc_apfloat::{Float, Round, Status, StatusAnd};

fn main() {
    let x = Quad::largest();

    let StatusAnd { status, value } = x.mul_r(x, Round::TowardZero);

    println!("value : {value:?}");
    println!("status: {status:?}");
}

Observed:

value : 1.18973149535723176508575932662800702E+4932(Normal | +[10384593717069655257060992658440191] * 2^16383)
status: Status(INEXACT)

Expected:

value : 1.18973149535723176508575932662800702E+4932(Normal | +[10384593717069655257060992658440191] * 2^16383)
status: Status(OVERFLOW | INEXACT)

This is related to the following LLVM issue: https://github.com/llvm/llvm-project/issues/220018

Start in src/ieee.rs at IeeeFloat::overflow_result and reproduce the provided Quad::largest multiplication with Round::TowardZero. Check the finite-result path and compare its status with the IEEE 754-2019 requirement, including the stated non-infinity case. Done means the result remains the largest finite value while the status includes both OVERFLOW and INEXACT.