Don't re-parse wasm for debuginfo (#2085)

* Don't re-parse wasm for debuginfo

This commit updates debuginfo parsing to happen during the main
translation of the original wasm module. This avoid re-parsing the wasm
module twice (at least the section-level headers). Additionally this
ties debuginfo directly to a `ModuleTranslation` which makes it easier
to process debuginfo for nested modules in the upcoming module linking
proposal.

The changes here are summarized by taking the `read_debuginfo` function
and merging it with the main module translation that happens which is
driven by cranelift. Some new hooks were added to the module environment
trait to support this, but most of it was integrating with existing hooks.

* Fix tests in debug crate

src/obj.rs

@@ -2,7 +2,7 @@ use anyhow::{anyhow, bail, Context as _, Result};
 use object::write::Object;
 use target_lexicon::Triple;
 use wasmtime::Strategy;
-use wasmtime_debug::{emit_dwarf, read_debuginfo};
+use wasmtime_debug::emit_dwarf;
 #[cfg(feature = "lightbeam")]
 use wasmtime_environ::Lightbeam;
 use wasmtime_environ::{
@@ -103,8 +103,7 @@ pub fn compile_to_obj(
         }
     };
 
-    let dwarf_sections = if debug_info {
-        let debug_data = read_debuginfo(wasm).context("failed to emit DWARF")?;
+    let dwarf_sections = if let Some(debug_data) = &translation.debuginfo {
         emit_dwarf(
             &*isa,
             &debug_data,