feat(ir): 添加MIR中间表示层并重构LIR相关代码

- 新增mir库模块，包含scc_mir、scc_mir_module、scc_mir_dump等组件
- 添加LIR到MIR的转换接口scc_lir2mir
- 定义MIR操作数类型和指令结构，支持虚拟寄存器、物理寄存器、立即数等
- 实现x86_64指令选择器，将LIR指令转换为MIR指令
- 重构LIR模块中函数参数命名，统一使用lir_module参数名
- 移除LIR中物理寄存器相关的代码和注释
- 更新cbuild.toml依赖配置，添加mir模块依赖

libs/ir/mir/cbuild.toml

@@ -0,0 +1,15 @@
+[package]
+name        = "scc_mir"
+version     = "0.1.0"
+authors     = []
+description = ""
+
+dependencies = [
+    { name = "scc_cfg", path = "../cfg" },
+    { name = "scc_lir", path = "../lir" },
+    { name = "scc_utils", path = "../../../runtime/scc_utils" },
+    { name = "tree_dump", path = "../../tree_dump" },
+    { name = "scc_mcode", path = "../../mcode" },
+]
+# features = {}
+# default_features = []