Move cranelift dependencies to wasmtime-environ (#669)

Groups all CL data structures into single dependency to be used accross wasmtime project.

crates/environ/src/data_structures.rs

@@ -0,0 +1,29 @@
+#![doc(hidden)]
+
+pub mod ir {
+    pub use cranelift_codegen::ir::{
+        types, AbiParam, ArgumentPurpose, Signature, SourceLoc, StackSlots, TrapCode, Type,
+        ValueLabel, ValueLoc,
+    };
+    pub use cranelift_codegen::ValueLabelsRanges;
+}
+
+pub mod settings {
+    pub use cranelift_codegen::settings::{builder, Configurable, Flags};
+}
+
+pub mod isa {
+    pub use cranelift_codegen::isa::{CallConv, RegUnit, TargetFrontendConfig, TargetIsa};
+}
+
+pub mod entity {
+    pub use cranelift_entity::{BoxedSlice, EntityRef, PrimaryMap};
+}
+
+pub mod wasm {
+    pub use cranelift_wasm::{
+        get_vmctx_value_label, DefinedFuncIndex, DefinedGlobalIndex, DefinedMemoryIndex,
+        DefinedTableIndex, FuncIndex, Global, GlobalIndex, GlobalInit, Memory, MemoryIndex,
+        SignatureIndex, Table, TableElementType, TableIndex,
+    };
+}