Support PHP 8.4 (#668)

Resolve #641

To support PHP 8.4, I've added tests for PHP 8.4.
I will add `Run checks on PHP 8.4` jobs as required to Settings.

FYI:
The deprecated usages reported in
#625 can not be checked
in this test if it is used in auto-generated files. Because
auto-generated files have a lot of phpstan error included others than
this, so we use phpstan only in non auto-generated files.

Author: eucyt

.github/workflows/php-checks.yml

@@ -12,14 +12,16 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        php: [8.1, 8.2, 8.3]
+        php: [8.1, 8.2, 8.3, 8.4]
         include:
           - php: 8.1
             analysis: true
           - php: 8.2
             analysis: true
           - php: 8.3
             analysis: true
+          - php: 8.4
+            analysis: true
 
     steps:
       - name: Checkout