Make Direct Assignments to CommonJS Exports Considered Literal Contexts

#39816

• In JavaScript, module.exports.yadda = ... is considered read-only already.
• What about module.exports = { yadda: ... }?
• This PR makes it so we consider that when we decide the types are literals or unique symbols.
• Technically a breaking change.
  • At earliest, 4.1
• This would be the only place where we infer an object literal to have readonly properties.
• Let's see how the user code suite works with this.
• Because it's only CommonJS, maybe we should just leave it alone.
• Probably merits no breakage if we see any.
• Merge otherwise.

Variadic Tuples in Promise.all

#39796

• With Promise.all, we have like 8 overloads.
• They don't handle functions with optional members or with rest elements.
  • Means you end up with a weakly typed result from Promise.all.
• Variadics can handle all these great cases that overloads can't!
• Technically a breaking change because people could give explicit type arguments.
• Sounds rare
  • 2 instances in VS Code
• This also brings up a question about the awaited type.
  • How many levels should the approximated Awaited type in the PR handle?
• We want T | Promise<T> to ensure that T is not a Promise.
  • But Promise itself can be constructed with an unconstrained type parameter.
• Will we ever solve this?
• Would be willing to try in 4.1.

Auto-Imports Slowdown

#38923

• We should always keep in mind that when these auto-magic features are supposed to make things really good, but then turn everything to crap.
• We could have a threshold of packages that are not already imported. If you have more than N packages, we don't do the work.
• We have a flag to turn things off: auto, off, and on.
  • Technically it's off, dependencies, devDependencies.
• We could do a low threshold - like 10 packages.
• Can we have editors communicate more than "loading JS/TS language features"?
  • Signaling exactly what we're working on to communicate that something can be turned on.
• Have to discuss some sort of mitigation plan