system: Replace repeated JS_DefineFunction with JS_DefineFunctions
object: Use JS_DefineFunctions as well
repo: Move version getting code to its own function

This makes the code a lot easier to read.
repo: Simplify namespace lookup code
importer: Split out the code that evaluates the script

from the one that defines it on the import object itself. We'll soon
use this to implement an alternate require(); syntax that aligns with
CommonJS.
importer: Remove finish_import

We already check for pending exceptions at the import_file level,
so we don't need to do it again. Also, the log message mentions
native modules, which can be confusing.
importer: Move import_file up here

We're going to use it to refactor load_module_init
importer: Replace load_module_init implementation with import_file
Support using GResource as a base search path for JS files

This commit changes the way files are imported inside GJS to use GIO,
transparently adding support for using a resource:/// search path to
lookup JS files in loaded GResources.

https://bugzilla.gnome.org/show_bug.cgi?id=703440