Preserve same vtable pointer when cloning raw waker, to fix Waker::will_wake
Fixes#121600.
As `@jkarneges` identified in https://github.com/rust-lang/rust/issues/121600#issuecomment-1963041051, the issue is two different const promotions produce two statics at different addresses, which may or may not later be deduplicated by the linker (in this case not).
Prior to #119863, the content of the statics was compared, and they were equal. After, the address of the statics are compared and they are not equal.
It is documented that `will_wake` _"works on a best-effort basis, and may return false even when the Wakers would awaken the same task"_ so this PR fixes a quality-of-implementation issue, not a correctness issue.
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