extract shared cairo-native-syscalls crate

Both cairo-native and sierra-emu now re-export the StarknetSyscallHandler
trait and supporting types (U256, Block/Tx/Execution Info v{1,2,3},
ResourceBounds, Secp256{k1,r1}Point) from the new
`cairo-native-syscalls` crate. The crate is workspace-local at the top
level (sibling to `test_utils/`).

The two crates' types are now nominally identical, so a single handler
impl can drive both runtimes without an adapter / bridge.

sierra-emu's previous inherent into_value/from_value methods (which
depend on sierra-emu's `Value` enum and can't follow the moved types)
become free functions in the new sub-module
`sierra_emu::starknet::value_conv`. Callers updated.

The per-type files under debug_utils/sierra-emu/src/starknet/* are
deleted now that the struct definitions live in the shared crate.

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

Author: avi-starkware

Cargo.lock

@@ -3,6 +3,7 @@ exclude = [
     "debug_utils/casm-data-flow",
 ]
 members = [
+    "cairo-native-syscalls",
     "debug_utils",
     "debug_utils/sierra-emu",
     "debug_utils/cairo-native-stress",
@@ -53,6 +54,7 @@ cairo-lang-test-runner = "~2.17.0-rc.4"
 cairo-lang-utils = "~2.17.0-rc.4"
 cairo-native-bin-utils.path = "binaries/cairo-native-bin-utils"
 cairo-native = { path = ".", version = "0.9.0-rc.6" }
+cairo-native-syscalls = { path = "cairo-native-syscalls", version = "0.9.0-rc.6" }
 clap = "4.5.23"
 colored = "2.1.0"
 criterion = "0.5.1"
@@ -128,6 +130,7 @@ testing = ["dep:cairo-lang-compiler", "dep:cairo-lang-filesystem"]
 [dependencies]
 aquamarine.workspace = true
 bumpalo.workspace = true
+cairo-native-syscalls.workspace = true
 cairo-lang-compiler = { workspace = true, optional = true }
 cairo-lang-filesystem = { workspace = true, optional = true }
 cairo-lang-lowering.workspace = true

Cargo.toml

@@ -0,0 +1,11 @@
+[package]
+name = "cairo-native-syscalls"
+version.workspace = true
+edition.workspace = true
+license.workspace = true
+repository.workspace = true
+description = "Shared StarknetSyscallHandler trait and supporting types for cairo-native and sierra-emu"
+
+[dependencies]
+serde = { workspace = true, features = ["derive"] }
+starknet-types-core = { workspace = true, features = ["std", "serde", "num-traits"] }