Make *-inl.h slim again

Inspired by me setting a breakpoint on a function and gdb telling me there are 12 locations...

The idea behind the *-inl.h files is to provide inline definitions of short functions. Large gobs of code don't belong in them because they negatively impact:

Compile times
Binary size (duplication)
Run-time performance (instruction cache pressure)

Rules of thumb:

Functions with few or infrequent callers should (judgment call) live in a .cc file
Functions over 4-5 lines that aren't template functions should live in a .cc file
Macros like CHECK(..) expand to multiple lines of code and should be counted as such

Good (short, many callers):

	inline v8::Isolate* IsolateData::isolate() const {
	return isolate_;
	}

Not good (big, only two infrequent callers):

	inline void Environment::AssignToContext(v8::Local<v8::Context> context,
	const ContextInfo& info) {
	context->SetAlignedPointerInEmbedderData(
	ContextEmbedderIndex::kEnvironment, this);
	// Used by Environment::GetCurrent to know that we are on a node context.
	context->SetAlignedPointerInEmbedderData(
	ContextEmbedderIndex::kContextTag, Environment::kNodeContextTagPtr);
	// Used to retrieve bindings
	context->SetAlignedPointerInEmbedderData(
	ContextEmbedderIndex::kBindingListIndex, &(this->bindings_));

	#if HAVE_INSPECTOR
	inspector_agent()->ContextCreated(context, info);
	#endif // HAVE_INSPECTOR

	this->async_hooks()->AddContext(context);
	}

Questionable (single infrequent caller):

	inline void Environment::TryLoadAddon(
	const char* filename,
	int flags,
	const std::function<bool(binding::DLib*)>& was_loaded) {
	loaded_addons_.emplace_back(filename, flags);
	if (!was_loaded(&loaded_addons_.back())) {
	loaded_addons_.pop_back();
	}
	}

The most commonly used *-inl.h files are:

$ find src -type f | xargs perl -ne 'print "$1\n" if /#\s*include "([^"]+-inl.h)"/' | sort | uniq -c | sort -r | head -9
  91 env-inl.h
  74 util-inl.h
  52 memory_tracker-inl.h
  42 base_object-inl.h
  35 async_wrap-inl.h
  29 debug_utils-inl.h
  19 threadpoolwork-inl.h
  18 node_process-inl.h
  15 stream_base-inl.h