Support ES2023 hashbang grammer

[p-bakker]

See https://github.com/tc39/proposal-hashbang

[CanadaHonk]

This is already supported for the most part with a few minor test262 edgecase failures. Just fixed 2 in #1341 :)

[tuchida]

I have two questions.

1. HashbangComment is supposed to start with #! according to the ECMA262 specification.
   https://tc39.es/ecma262/2023/#sec-hashbang
   However, Rhino only checks #. I thought they were not ES2023 compliant.
   

   rhino/toolsrc/org/mozilla/javascript/tools/shell/Main.java

   Lines 564 to 567 in f24883f

   	// Support the executable script #! syntax: If
   	// the first line begins with a '#', treat the whole
   	// line as a comment.
   	if (strSrc.length() > 0 && strSrc.charAt(0) == '#') {

2. The feature of the org.mozilla.javascript.tools.shell.Main class is only enable in shell mode. Should HashbangComment be enabled when using Rhino from Java source code?

[CanadaHonk]

Good catch, I didn't spot that on a quick first look. It should check the next char and be copied into the main parser (most likely).

[p-bakker]

Agree with @tuchida that Hashbang should also work when using the Rhino engine directly, so not through the Shell