core::ptr: deduplicate more method docs

[lolbinarycat]

used rg -Fxf library/core/src/ptr/{const,mut}_ptr.rs to find duplicated doc comments, and diff -u after copying them to files to ensure they are actually identical.

sed 's| */// *||' was then used to translate the doc comments to plain markdown.

part of #139190

[rust-log-analyzer]

The job mingw-check-2 failed! Check out the build log: (web) (plain)

Click to see the possible cause of the failure (guessed by this bot)

[RUSTC-TIMING] build_script_build test:false 0.389
error: unresolved link to `as_uninit_slice_mut`
    --> library/core/src/ptr/mut_ptr.rs:1895:43
     |
1895 |     /// For the mutable counterpart see [`as_uninit_slice_mut`].
     |                                           ^^^^^^^^^^^^^^^^^^^ no item named `as_uninit_slice_mut` in scope
     |
     = help: to escape `[` and `]` characters, add '\' before them like `\[` or `\]`
     = note: `-D rustdoc::broken-intra-doc-links` implied by `-D warnings`
     = help: to override `-D warnings` add `#[allow(rustdoc::broken_intra_doc_links)]`

error: could not document `core`
warning: build failed, waiting for other jobs to finish...
[RUSTC-TIMING] core test:false 31.434
Command has failed. Rerun with -v to see more details.
Build completed unsuccessfully in 0:00:34
  local time: Fri Jun  6 01:31:19 UTC 2025
  network time: Fri, 06 Jun 2025 01:31:19 GMT
##[error]Process completed with exit code 1.
Post job cleanup.