Use asynchronous GET requests / Replace xmlhttprequest-ts with fetch API for module loading

[Yongbeom-Kim]

Continued from #1340

Problem

• Currently, js-slang uses the xmlhttprequest-ts package to make GET requests to retrieve module data.
• The package has not had any updates/releases in the past 5 years, and it seems safe to say that this package should be deprecated in favour of something like fetch instead, as suggested by a contributor(?) Retire project, and archive it. hmoog/xmlhttprequest-ts#6
• It's also worthy of noting that synchronous/blocking XMLHttpRequests (as is being done in js-slang) are deprecated
• Well, it makes sense that the get request should be asynchronous/non-blocking?

Proposal

• Refactor js-slang to load modules asynchronously (with async functions and promises)
• Replace all XMLHttpRequest GET requests with fetch requests
• Use top-level await to load modules (if needed)
  • I don't think this is a big issue, noting that top-level await is supported on all browsers
  • This also requires bumping tsconfig.json to:

{
  "compilerOptions": {
    "module": "esnext" (or system),
    "target": "es2017",
}

[leeyi45]

As part of this, I'm thinking we delegate loading of tabs to the frontend. Tabs are a frontend only concept, so I don't think it makes sense for js-slang to do the loading.

Related to this issue

I've done some looking into this, most of the runners aren't affected, except maybe the interpreter, not sure if that one supports async evaluation

[RichDom2185]

I would say this is an issue of high enough priority; I will pin it to the top of our issues list.

[leeyi45]

This transition is actually almost complete. Most of the features surrounding module loading are asynchronous, namely

• Loading the module manifest
• Module Documentation
• Transpiler
• Stepper

The two remaining areas of concern are:

• The EC-Evaluator: Refer to my comment on this
• The regular interpreter, which is due to be removed as per Remove src/interpreter/interpreter.ts #1476
  Both of which still require the synchronous versions