IDL compiler: Use v8AtomicString instead of v8::String::NewFromUtf8 (remaining places)

Followup to:
Use v8AtomicString instead of v8::String::NewFromUtf8
https://codereview.chromium.org/116983005/

There were a few places in the Perl code that hadn't changed:
v8::String::NewFromUtf8(isolate, "{NAME}", v8::String::kInternalizedString)
=>
v8AtomicString(isolate, "{NAME}")
...but had been updated in the Python code.

This syncs the Perl code to also make these changes.

Review URL: https://codereview.chromium.org/116933006

git-svn-id: svn://svn.chromium.org/blink/trunk@164572 bbb929c8-8fbe-4397-9dbb-9b2b20218538