Rollup merge of #79174 - taiki-e:std-future, r=Mark-Simulacrum

Make std::future a re-export of core::future

After 1a764a7, there are no `std::future`-specific items (except for `cfg(bootstrap)` items removed in 93eed40). So, instead of defining `std` own module, we can re-export the `core::future` directly.

Author: jonas-schievink

library/std/src/future.rs

@@ -406,6 +406,8 @@ pub use core::cmp;
 pub use core::convert;
 #[stable(feature = "rust1", since = "1.0.0")]
 pub use core::default;
+#[stable(feature = "futures_api", since = "1.36.0")]
+pub use core::future;
 #[stable(feature = "rust1", since = "1.0.0")]
 pub use core::hash;
 #[stable(feature = "core_hint", since = "1.27.0")]
@@ -505,9 +507,6 @@ pub mod task {
     pub use alloc::task::*;
 }
 
-#[stable(feature = "futures_api", since = "1.36.0")]
-pub mod future;
-
 // Platform-abstraction modules
 #[macro_use]
 mod sys_common;