feature #47730 Ban DateTime from the codebase (WebMamba)

This PR was squashed before being merged into the 6.2 branch.

Discussion
----------

Ban DateTime from the codebase

| Q             | A
| ------------- | ---
| Branch?       | 6.2
| Bug fix?      | no
| New feature?  | yes
| Deprecations? | yes
| Tickets       | #47580
| License       | MIT
| Doc PR        | symfony

As discuss in this issue, the purpose of this PR is to remove DateTime from the code base in favor to DateTimeImmutable. I will process it component by component. Feel free to discuss!

Commits
-------

689385a83f Ban DateTime from the codebase

Author: fabpot

Tests/TimezonesTest.php

@@ -666,7 +666,7 @@ public function provideCountries(): iterable
 
     public function testGetRawOffsetChangeTimeCountry()
     {
-        $this->assertSame(7200, Timezones::getRawOffset('Europe/Paris', (new \DateTime('2022-07-16 00:00:00+00:00'))->getTimestamp()));
-        $this->assertSame(3600, Timezones::getRawOffset('Europe/Paris', (new \DateTime('2022-02-16 00:00:00+00:00'))->getTimestamp()));
+        $this->assertSame(7200, Timezones::getRawOffset('Europe/Paris', (new \DateTimeImmutable('2022-07-16 00:00:00+00:00'))->getTimestamp()));
+        $this->assertSame(3600, Timezones::getRawOffset('Europe/Paris', (new \DateTimeImmutable('2022-02-16 00:00:00+00:00'))->getTimestamp()));
     }
 }

Tests/Util/GitRepositoryTest.php

@@ -56,7 +56,7 @@ public function testItClonesTheRepository()
         $this->assertSame(self::REPO_URL, $git->getUrl());
         $this->assertMatchesRegularExpression('#^[0-9a-z]{40}$#', $git->getLastCommitHash());
         $this->assertNotEmpty($git->getLastAuthor());
-        $this->assertInstanceOf(\DateTime::class, $git->getLastAuthoredDate());
+        $this->assertInstanceOf(\DateTimeImmutable::class, $git->getLastAuthoredDate());
         $this->assertStringMatchesFormat('v%s', $git->getLastTag());
         $this->assertStringMatchesFormat('v3%s', $git->getLastTag(function ($tag) { return str_starts_with($tag, 'v3'); }));
     }

Util/GitRepository.php

@@ -64,9 +64,9 @@ public function getLastAuthor(): string
         return $this->getLastLine($this->execInPath('git log -1 --format="%an"'));
     }
 
-    public function getLastAuthoredDate(): \DateTime
+    public function getLastAuthoredDate(): \DateTimeImmutable
     {
-        return new \DateTime($this->getLastLine($this->execInPath('git log -1 --format="%ai"')));
+        return new \DateTimeImmutable($this->getLastLine($this->execInPath('git log -1 --format="%ai"')));
     }
 
     public function getLastTag(callable $filter = null): string