Implements https://github.com/tc39/ecma262/pull/2154, which allows
module export names to be string literals.

Semantics highlights:
  - It is a SyntaxError for string literal export names to have unpaired
    UTF16 surrogates.
  - It is a SyntaxError for string literal export names to be used as
    the local name without being followed by a 'from' clause. For example,
    `export { "foo" }` and `export { "foo" as "bar" }` are errors, but
    `export { "foo" } from "./module.js"` is allowed.

The remaining failing test262 test is wrong:
https://github.com/tc39/test262/issues/2866

Bug: v8:10964
Change-Id: Ib3e06e1ee6b3f1b60ed7f24e21902e17ddfc0351
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2482335
Commit-Queue: Shu-yu Guo <syg@chromium.org>
Reviewed-by: Leszek Swirski <leszeks@chromium.org>
Reviewed-by: Marja Hölttä <marja@chromium.org>
Cr-Commit-Position: refs/heads/master@{#70692}