src: initial support for ESM in embedder API

[joyeecheung]

This patch extends LoadEnvironment to support loading ES modules, and adds the following new types:

enum class ModuleFormat : uint8_t {
  kCommonJS,
  kModule,
};

// Data for specifying an entry point script for LoadEnvironment().
// This class uses an opaque layout to allow future additions without
// breaking ABI. Use the setter methods to configure the entry point.
class ModuleData {
  void set_source(std::string_view source);
  void set_format(ModuleFormat format);
  void set_resource_name(std::string_view name);

  std::string_view source() const;
  ModuleFormat format() const;
  std::string_view resource_name() const;
};

class StartExecutionCallbackInfoWithModule {
  void set_env(Environment* env);
  void set_process_object(v8::Local<v8::Object> process_object);
  void set_native_require(v8::Local<v8::Function> native_require);
  void set_run_module(v8::Local<v8::Function> run_module);
  void set_data(void* data);

  Environment* env();
  v8::Local<v8::Object> process();
  v8::Local<v8::Function> native_require();
  v8::Local<v8::Function> run_module();
  void* data();
};

And two new LoadEnvironment() overloads:

// Run entry point with ModuleData configuration
MaybeLocal<Value> LoadEnvironment(
    Environment* env,
    const ModuleData* entry_point,
    EmbedderPreloadCallback preload = nullptr);

// Callback-based with new StartExecutionCallbackInfoWithModule
MaybeLocal<Value> LoadEnvironment(
    Environment* env,
    StartExecutionCallbackWithModule cb,
    EmbedderPreloadCallback preload = nullptr,
    void* callback_data = nullptr);

Notes about the run_module function:

• The run_cjs function is renamed to run_module and now accepts
  three arguments: (source, format, resourceName) where format
  corresponds to ModuleFormat values. This keeps the old
  StartExecutionCallback backward-compatible, and reuses this new
  function for StartExecutionCallbackWithModule.
• ESM entry points return the module namespace object, CJS entry
  points continue to return the wrapper's return value.

The following are left as TODO for follow-up PRs.

• Support for import() and import.meta
• Support for SEA: I have a branch here to support ESM in SEA via the new API.
• Support for snapshot: this requires integration of ModuleWrap objects
• Support for code cache: needs more plumbing for v8::Module cache

Refs: #53565

[nodejs-github-bot]

Review requested:

• @nodejs/startup

[joyeecheung]

cc @nodejs/embedders

[codecov]

Codecov Report

❌ Patch coverage is 89.94975% with 20 lines in your changes missing coverage. Please review.
✅ Project coverage is 89.78%. Comparing base (83893bb) to head (e5475d4).
⚠️ Report is 17 commits behind head on main.

Files with missing lines	Patch %	Lines
lib/internal/main/embedding.js	82.50%	14 Missing ⚠️
src/api/environment.cc	94.38%	4 Missing and 1 partial ⚠️
src/node.cc	92.30%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@           Coverage Diff            @@
##             main   #61548    +/-   ##
========================================
  Coverage   89.78%   89.78%            
========================================
  Files         672      672            
  Lines      203809   203916   +107     
  Branches    39183    39182     -1     
========================================
+ Hits       182980   183077    +97     
- Misses      13166    13183    +17     
+ Partials     7663     7656     -7     

Files with missing lines	Coverage Δ
src/node.h	95.91% <ø> (ø)
src/node_internals.h	82.35% <ø> (ø)
src/node_main_instance.cc	90.14% <100.00%> (ø)
src/node_modules.cc	79.80% <100.00%> (+0.75%)	⬆️
src/node_worker.cc	81.60% <100.00%> (-0.10%)	⬇️
src/node.cc	76.21% <92.30%> (+0.12%)	⬆️
src/api/environment.cc	79.14% <94.38%> (+2.29%)	⬆️
lib/internal/main/embedding.js	85.08% <82.50%> (-3.91%)	⬇️

... and 27 files with indirect coverage changes

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[joyeecheung]

I don't think this is semver-major - notice none of the existing tests need updating, as the new overloads are backward compatible.

(I would be worth at some point deprecating the older overloads, maybe before March for 26, because the older types are prone to ABI breakage whenever we try to add more features, but that can be a separate PR).

[joyeecheung]

hmm, noticed that I accidentally changed the original overloads - updated to remove the changes. This should be now fully backward compatible.