Rollup merge of #149744 - lemire:main, r=Mark-Simulacrum

test: update duplicate many_digits test to use f64 instead of f32

Replace the f32 test case with an f64 equivalent to improve coverage for parsing large digit counts in double-precision floating-point conversion. Specifically, this PR updates the `many_digits` test in `library/coretests/tests/num/dec2flt/parse.rs` to test f64 (double-precision) parsing instead of f32 (single-precision).

The test verifies that decimal strings with an excessive number of digits (beyond `Decimal::MAX_DIGITS`) are parsed correctly, ensuring proper truncation of insignificant digits. Previously, the same test was repeated twice (see comment https://github.com/rust-lang/rust/pull/86761#issuecomment-3623334228 by `@Viatorus).`

## Changes

- Replaced the duplicated f32 test case with an equivalent f64 test case.
- Updated the expected bit pattern and input string to a very long decimal with many trailing zeros, testing the limits of f64 precision.

library/coretests/tests/num/dec2flt/parse.rs

@@ -204,8 +204,8 @@ fn many_digits() {
         "1.175494140627517859246175898662808184331245864732796240031385942718174675986064769972472277004271745681762695312500000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000e-38"
     );
     assert_float_result_bits_eq!(
-        0x7ffffe,
-        f32,
-        "1.175494140627517859246175898662808184331245864732796240031385942718174675986064769972472277004271745681762695312500000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000e-38"
+        0x7ffffffffffffe,
+        f64,
+        "2.8480945388892171379514712013899006561925415836684281158317117472799232118121416898288331376688117187382156519616555919469923055562697333532151065976805407006156569379201589813489881051279092585294136284133893120582268661680741374638184352784785121471797815387841323043061183721896440504100014432145713413240639315126126485370149254502658324386101932795656342787961697168715161403422599767855490566539165801964388919848888980308652852766053138934233069066651644954964960514065582826296567812754916294792554028205611526494813491373571799099361175786448799007387647056059512705071170383000860694587462575533337769237800154235626508997957207085308694919708914563870082480025309479610576861709891209343110514894825624524442569257542956506767950486391782760620117187500000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000e-306"
     );
 }