Convert compilation artifacts to just bytes (#3239)

* Convert compilation artifacts to just bytes

This commit strips the `CompilationArtifacts` type down to simply a list
of bytes. This moves all extra metadata elsewhere to live within the
list of bytes itself as `bincode`-encoded information.

Small affordance is made to avoid an in-process
serialize-then-deserialize round-trip for use cases like `Module::new`,
but otherwise this is mostly just moving some data around.

* Rename data section to `.rodata.wasm`

crates/jit/src/lib.rs

@@ -29,7 +29,8 @@ mod unwind;
 
 pub use crate::code_memory::CodeMemory;
 pub use crate::instantiate::{
-    CompilationArtifacts, CompiledModule, ModuleCode, SetupError, SymbolizeContext, TypeTables,
+    CompilationArtifacts, CompiledModule, CompiledModuleInfo, ModuleCode, SetupError,
+    SymbolizeContext, TypeTables,
 };
 pub use crate::link::link_module;
 pub use profiling::*;