Allow serializing all cranelift-module data structures (#6172)

* Remove ModuleCompiledFunction

The same information can be retrieved using

ctx.compiled_code().unwrap().code_info().total_size

In addition for Module implementations that don't immediately compile the
given function there is no correct value that can be returned.

* Don't give anonymous functions and data objects an internal name

This internal name can conflict if a module is serialized and then
deserialized into another module. It also wasn't used by any of the
Module implementations anyway.

* Allow serializing all cranelift-module data structures

This allows a Module implementation to serialize it's internal state and
deserialize it in another compilation session. For example to implement
LTO or to load the module into cranelift-interpreter.

* Use expect

Cargo.lock

@@ -747,6 +747,7 @@ dependencies = [
  "cranelift-codegen",
  "cranelift-control",
  "hashbrown 0.13.2",
+ "serde",
 ]
 
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