fix: use PHP 8 concatenation precedence in the pretty printer

The precedence table gave "." the same precedence as "+" and "-", which is
the PHP 7 ordering. PHP 8.0 lowered "." below the arithmetic and shift
operators, so printing ('abc' . 1) + 2 produced 'abc' . 1 + 2, which PHP 8
reparses as 'abc' . (1 + 2). The same applied to "-", "<<" and ">>".

The printer already targets a specific PHP version and already varies
parenthesization by version, so select the concatenation precedence the same
way: for a target of PHP 8.0 or newer, place "." between the shift operators
and the pipe operator, matching the PHP8 block of grammar/php.y. Targets below
8.0 keep the PHP 7 table, which is correct for them and produces unchanged
output.

Fixes #1041

lib/PhpParser/PhpVersion.php

@@ -172,4 +172,12 @@ class PhpVersion {
     public function supportsNewDereferenceWithoutParentheses(): bool {
         return $this->id >= 80400;
     }
+
+    /**
+     * Whether the concatenation operator has lower precedence than the arithmetic and shift
+     * operators. Prior to PHP 8.0, "." had the same precedence as "+" and "-".
+     */
+    public function hasLowerConcatPrecedence(): bool {
+        return $this->id >= 80000;
+    }
 }