Disallow ambiguous attributes on expressions (take 2)

[petrochenkov]

Previous reverted attempt - #124099.
cc #159581

TODO:

• Desription, crater run
• Figure out whether addressing Stabilize attributes on closure and method call expressions #159581 (comment) is necessary if macros in expr/stmt positions are not stabilized

[rustbot]

The parser was modified, potentially altering the grammar of (stable) Rust
which would be a breaking change.

cc @fmease

[rustbot]

r? @chenyukang

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[rust-log-analyzer]

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

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

---- [codegen] tests/codegen-llvm/loop-attrs/unroll-loop-metadata.rs stdout ----
------rustc stdout------------------------------

------rustc stderr------------------------------
error: suspicious attribute: parse_expr_assoc_rest_with rhs
##[error]  --> /checkout/tests/codegen-llvm/loop-attrs/unroll-loop-metadata.rs:53:24
   |
53 |     let _return = (1 + #[unroll(never)]
   |                        ^^^^^^^^^^^^^^^^

error: aborting due to 1 previous error


------------------------------------------

error: compilation failed!
status: exit status: 1
command: env -u RUSTC_LOG_COLOR RUSTC_ICE="0" RUST_BACKTRACE="short" "/checkout/obj/build/x86_64-unknown-linux-gnu/stage1/bin/rustc" "/checkout/tests/codegen-llvm/loop-attrs/unroll-loop-metadata.rs" "-Zthreads=1" "-Zsimulate-remapped-rust-src-base=/rustc/FAKE_PREFIX" "-Ztranslate-remapped-path-to-local-path=no" "-Z" "ignore-directory-in-diagnostics-source-blocks=/cargo" "-Z" "ignore-directory-in-diagnostics-source-blocks=/checkout/vendor" "--sysroot" "/checkout/obj/build/x86_64-unknown-linux-gnu/stage1" "--target=wasm32-wasip1" "--check-cfg" "cfg(test,FALSE)" "-O" "-Cdebug-assertions=no" "-Zcodegen-source-order" "--emit" "llvm-ir" "-C" "prefer-dynamic" "-o" "/checkout/obj/build/x86_64-unknown-linux-gnu/test/codegen-llvm/loop-attrs/unroll-loop-metadata/unroll-loop-metadata.ll" "-A" "internal_features" "-A" "incomplete_features" "-A" "unused_parens" "-A" "unused_braces" "-Crpath" "-Cdebuginfo=0" "-O" "-Cno-prepopulate-passes"
stdout: none
--- stderr -------------------------------
error: suspicious attribute: parse_expr_assoc_rest_with rhs
##[error]  --> /checkout/tests/codegen-llvm/loop-attrs/unroll-loop-metadata.rs:53:24
   |
53 |     let _return = (1 + #[unroll(never)]
   |                        ^^^^^^^^^^^^^^^^

error: aborting due to 1 previous error
------------------------------------------