Added uuid()

Satisfies a common use case and benchmarks faster by ~15%...

Instead of:

use UUID ':all';
sub myuuid {
    my ( $uuid, $str );
    generate_uuid( $uuid );
    unparse_uuid( $str );
    return $str;
}
my $uuid_str = myuuid();

Replace with:

use UUID 'uuid';
my $uuid_str = uuid();

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