Regex literals with invalid `\N{...}` names should not compile

UTS18 makes a distinction between providing an invalid name in a Unicode property character class (\p{name=...}) and an individual named character (\N{...}). If a programmer uses an invalid name in a property character class, the expression should compile and that character class should simply not match anything:

"🐯".contains(/\p{name=TIGER FACE}/)     // true
"🐯".contains(/\p{name=TIEGR FACE}/)     // false

However, an invalid name given in a \N{...} named character should be a syntax/compilation error:

"🐯".contains(/\N{TIEGR FACE}/)          // error: Invalid Unicode scalar name

See https://unicode.org/reports/tr18/#Individually_Named_Characters

Start by tracing how the regex engine parses and validates \N{...} names, then compare that behavior with the documented \p{name=...} handling in UTS18. Done means an invalid name in \N{...} is rejected as a compilation error, while an invalid property name remains compilable and matches nothing.