Show AtomicU128/AtomicI128 in std docs regardless of target

[Mtfl0n]

Fixes #130474

Ensures AtomicU128 and AtomicI128 appear in documentation even when docs are built for targets without native 128-bit atomic support (like x86_64-unknown-linux-gnu). The fix adds cfg(doc) to existing conditional compilation checks.

Changes:

• Added cfg(doc) to #[cfg(target_has_atomic_load_store = "128")]
• Added cfg(doc) to internal cfg(target_has_atomic = "128") in atomic_int! macro

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[rust-log-analyzer]

The job aarch64-gnu-llvm-19-2 failed! Check out the build log: (web) (plain enhanced) (plain)

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[RUSTC-TIMING] ____ test:false 0.024
[COPY] stdlib source
[PATCH] "stdlib" <- "0027-stdlib-128bit-atomic-operations.patch"
error: patch failed: library/core/src/sync/atomic.rs:3585
error: library/core/src/sync/atomic.rs: patch does not apply
hint: Use 'git am --show-current-patch=diff' to see the failed patch
hint: When you have resolved this problem, run "git am --continue".
hint: If you prefer to skip this patch, run "git am --skip" instead.
hint: To restore the original branch and stop patching, run "git am --abort".
hint: Disable this message with "git config advice.mergeConflict false"
Patch failed at 0001 Disable 128bit atomic operations
cd "/checkout/obj/build/aarch64-unknown-linux-gnu/stage1-tools/cg_clif/build/stdlib" && "git" "-c" "user.name=Dummy" "-c" "[email protected]" "-c" "core.autocrlf=false" "-c" "commit.gpgSign=false" "am" "/checkout/compiler/rustc_codegen_cranelift/patches/0027-stdlib-128bit-atomic-operations.patch" "-q" exited with status ExitStatus(unix_wait_status(32768))
Command has failed. Rerun with -v to see more details.
Build completed unsuccessfully in 0:11:32
  local time: Fri Jul  4 17:25:45 UTC 2025
  network time: Fri, 04 Jul 2025 17:25:45 GMT
##[error]Process completed with exit code 1.
Post job cleanup.