blockifier: re-add new_from_emu for out-of-tree benchmarking branch

`new_from_emu` was deleted in 88b68af after Cursor flagged it as
unused. Restore it (with a doc comment naming the planned consumer)
so the benchmarking / replay tooling — which will live as a feature
branch and is not expected to merge here — can reach it without
patching this file. No `#[expect(dead_code)]` needed: `dead_code`
doesn't fire on `pub fn` in a library crate.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: avi-starkware

crates/blockifier/src/execution/native/contract_class.rs

@@ -4,6 +4,8 @@ use std::sync::Arc;
 
 #[cfg(feature = "with-libfunc-profiling")]
 use cairo_native::executor::AotWithProgram;
+#[cfg(feature = "sierra-emu")]
+use cairo_native::executor::EmuContractInfo;
 use cairo_native::executor::{AotContractExecutor, ContractExecutor};
 use starknet_api::contract_class::compiled_class_hash::HashableCompiledClass;
 use starknet_api::core::EntryPointSelector;
@@ -37,6 +39,17 @@ impl NativeCompiledClassV1 {
         Self(Arc::new(contract))
     }
 
+    /// Initialize a compiled class backed by the sierra-emu interpreter instead of the AOT
+    /// executor. Intended for the out-of-tree benchmarking / replay feature branch — those
+    /// tools are not expected to merge into this repo and will consume this constructor
+    /// from a fork. `pub` so a fork can reach it without patching this file.
+    #[cfg(feature = "sierra-emu")]
+    pub fn new_from_emu(info: EmuContractInfo, casm: CompiledClassV1) -> NativeCompiledClassV1 {
+        let contract = NativeCompiledClassV1Inner::new(info.into(), casm);
+
+        Self(Arc::new(contract))
+    }
+
     /// Like [`Self::new`], but also stores the Sierra `Program` (via the cairo-native
     /// [`AotWithProgram`] pairing) so [`cairo_native::ContractExecutor::run_with_profile`]
     /// can resolve libfunc samples. Only callable when the `with-libfunc-profiling`