test(datetime): update datetime builtin class tests with explicit format parsing

- Replace dynamic current time test with fixed datetime format parsing
- Change DateTime::createFromFormat call to parse specific datetime string '2024-02-03 04:05:06'
- Update expected output from variable format to fixed '2024-02-03 04:05:06'
- Remove variable timestamp output and replace with predictable datetime string
- Modify static call test to use explicit datetime string instead of current time

- Add explicit string casting for Stringable objects when passed to internal string functions
- Update numeric values with explicit (string) casts before using in string functions
- Adjust test expectations to match strict type behavior for string operations

tests/compiler/basic/datetime_builtin_class.phpt

@@ -35,9 +35,9 @@ $date4 = new DateTime('2023-12-31');
 $interval = $date3->diff($date4);
 echo $interval->days . " days\n";
 
-// Test static create methods
-$now = DateTime::createFromFormat('U', time());
-echo $now->format('Y-m-d H:i:s') . "\n";
+// Test parsing a datetime string with an explicit format.
+$parsed = DateTime::createFromFormat('Y-m-d H:i:s', '2024-02-03 04:05:06');
+echo $parsed->format('Y-m-d H:i:s') . "\n";
 
 // Test add/subtract intervals
 $date->add(new DateInterval('P1D')); // Add 1 day
@@ -57,8 +57,8 @@ echo $date->format('r') . "\n"; // RFC 2822 format
 2024-01-01 12:00:00
 2024-01-01 12:00:00 UTC
 364 days
-%d-%d-%d %d:%d:%d
+2024-02-03 04:05:06
 2024-01-02 12:00:00
 2024-01-01 12:00:00
 2024-01-01T12:00:00+00:00
-Mon, 01 Jan 2024 12:00:00 +0000
+Mon, 01 Jan 2024 12:00:00 +0000

tests/compiler/magic_methods/invoke-and-tostring.phpt

@@ -41,7 +41,9 @@ function main(): void {
     echo $greet("World") . "\n";
     echo $greet . "\n";
 
-    echo strlen($double) . "\n";
+    // TypePHP is always strict; Stringable objects require an explicit cast
+    // when passed to an internal function with a string parameter.
+    echo strlen((string) $double) . "\n";
 }
 ?>
 --EXPECT--

tests/compiler/static/static-call.phpt

@@ -4,6 +4,6 @@ static calls
 <?php
 $cls = 'DateTime';
 $method = 'createFromFormat';
-$now = $cls::$method('U', time());
+$date = $cls::$method('Y-m-d H:i:s', '2024-02-03 04:05:06');
 ?>
 --EXPECTF--

tests/compiler/string_method/to-str.phpt

@@ -1,12 +1,12 @@
 --TEST--
-any
+Explicit numeric-to-string casts work with string functions in strict mode
 --FILE--
 <?php
 ini_set('precision', 17);
-$s = 12345678;
+$s = (string) 12345678;
 var_dump(strlen($s));
 var_dump(strrev($s));
-var_dump(strlen(3.1415926));
+var_dump(strlen((string) 3.1415926));
 ?>
 --EXPECT--
 int(8)