Hex escapes in strings only support ASCII range

Escaped strings [1] fail on hex values greater than \x7f with a factually incorrect error message:

$ psql --command "select E'\x80';"
ERROR: invalid byte sequence for encoding "UTF8": 0x80

$ psql --version
psql (PostgreSQL) 13.1

I was able to reproduce this bug on psql 10.

Workaround:

$ psql --command "select E'\u0080';"
?column?
----------
\u0080
(1 row)

1: https://www.postgresql.org/docs/13/sql-syntax-lexical.html#id-1.5.3.5.9.5.3