LibJS: Use the source offset to sort imports in module

Using source offsets directly means we don't have to synthesize any
SourceRanges and circumvents that SourceRange returns invalid values for
the last range of a file.

Userland/Libraries/LibJS/AST.h

@@ -54,6 +54,7 @@ public:
     virtual void dump(int indent) const;
 
     [[nodiscard]] SourceRange source_range() const;
+    u32 start_offset() const { return m_start_offset; }
 
     void set_end_offset(Badge<Parser>, u32 end_offset) { m_end_offset = end_offset; }
 

Userland/Libraries/LibJS/SourceTextModule.cpp

@@ -47,27 +47,26 @@ static Vector<ModuleRequest> module_requests(Program& program, Vector<String> co
     // A List of all the ModuleSpecifier strings used by the module represented by this record to request the importation of a module.
     // Note: The List is source text occurrence ordered!
     struct RequestedModuleAndSourceIndex {
-        u64 source_index { 0 };
+        u32 source_offset { 0 };
         ModuleRequest* module_request { nullptr };
     };
 
     Vector<RequestedModuleAndSourceIndex> requested_modules_with_indices;
 
-    for (auto& import_statement : program.imports()) {
-        requested_modules_with_indices.empend(import_statement.source_range().start.offset, &import_statement.module_request());
-    }
+    for (auto& import_statement : program.imports())
+        requested_modules_with_indices.empend(import_statement.start_offset(), &import_statement.module_request());
 
     for (auto& export_statement : program.exports()) {
         for (auto& export_entry : export_statement.entries()) {
             if (!export_entry.is_module_request())
                 continue;
-            requested_modules_with_indices.empend(export_statement.source_range().start.offset, &export_statement.module_request());
+            requested_modules_with_indices.empend(export_statement.start_offset(), &export_statement.module_request());
         }
     }
 
     // Note: The List is source code occurrence ordered. https://tc39.es/proposal-import-assertions/#table-cyclic-module-fields
     quick_sort(requested_modules_with_indices, [&](RequestedModuleAndSourceIndex const& lhs, RequestedModuleAndSourceIndex const& rhs) {
-        return lhs.source_index < rhs.source_index;
+        return lhs.source_offset < rhs.source_offset;
     });
 
     Vector<ModuleRequest> requested_modules_in_source_order;