3.1.35+ contains NUL characters in JS

[RReverser]

In 3.1.35+ output seems to have escape sequences unescaped. It's hard to demonstrate by copy-pasting the code so I'll paste screenshot from an editor that shows that a comment on UTF8ToString now has a literal NUL (0) character:

and this is what it looked like before:

This caused problems in a C program that reads the JS file as a string and then tries to process it as a C string (that is, by stopping at said NUL character).

I narrowed it down to #19097 which moved code & comments into JS strings, but now that \0 is inside a JS string, it gets unescaped by the engine: f188340#diff-9b6499e625a2216c99e6a18e621462ba263fc408745bd38487fb9cefef61e1d0R104 cc @sbc100