This PR was merged into the 3.4 branch.Discussion----------[Translator] Fix wrong dump for PO files| Q             | A| ------------- | ---| Branch?       | 3.4| Bug fix?      | yes| New feature?  | no| BC breaks?    | no| Deprecations? | no| Tests pass?   | yes| Fixed tickets || License       | MIT| Doc PR        |When working on#30909 I encountered this bug.Currently the tests were passing, because the po fixture file contained only one translation.Commits-------b54abfc Fix wrong dump for PO files

This PR was merged into the 4.3-dev branch.Discussion----------[Translator] Add comments when dumping po files| Q             | A| ------------- | ---| Branch?       | master| Bug fix?      | no| New feature?  | yes| BC breaks?    | no| Deprecations? | no| Tests pass?   | ?    <!-- please add some, will be required by reviewers -->| Fixed tickets |#29962| License       | MIT| Doc PR        |This code```php$catalogue = new MessageCatalogue('fr');$dumper = new PoFileDumper();$catalogue->set('key.one', 'First key', 'custom');$catalogue->setMetadata('key.one', ['sources' => 'src/file_1', 'comments' => 'Comment', 'flags' => 'fuzzy'], 'custom');$catalogue->set('key.second', 'Second key', 'custom');$catalogue->setMetadata('key.second', ['sources' => ['src/file_1', 'src/file_2'], 'comments' => ['Comment 1', 'Comment 2'], 'flags' => ['fuzzy', 'another']], 'custom');$dumper->dump($catalogue, [    'path' => 'xxx',]);```Will produces this output:```msgid ""msgstr """Content-Type: text/plain; charset=UTF-8\n""Content-Transfer-Encoding: 8bit\n""Language: fr\n"# Comment#, fuzzy#: src/file_1msgid "key.one"msgstr "First key"# Comment 1# Comment 2#, fuzzy,another#: src/file_1 src/file_2msgid "key.second"msgstr "Second key"```Commits-------31b3a55 Add comments when dumping po files

This PR was merged into the 4.3-dev branch.Discussion----------[Translator] Add sources when dumping qt files| Q             | A| ------------- | ---| Branch?       | master| Bug fix?      | no| New feature?  | yes| BC breaks?    | no| Deprecations? | no| Tests pass?   | yes| Fixed tickets || License       | MIT| Doc PR        |This PR implements similar functionality as#30909, but for Qt files. Currently, only the Qt element `location` is supported, so only `sources` metadata is included in the dump.Commits-------ff7577d Add sources when dumping qt files

…php files (Stadly)This PR was squashed before being merged into the 4.3-dev branch (closes#31249).Discussion----------[Translator] Set sources when extracting strings from php files| Q             | A| ------------- | ---| Branch?       | master| Bug fix?      | no| New feature?  | yes| BC breaks?    | no| Deprecations? | no| Tests pass?   | yes| Fixed tickets || License       | MIT| Doc PR        |Set metadata about filenames and line numbers when extracting translatable strings from php files. This PR complements#30909 and#31248, as those PRs implement support for dumping the filenames and line numbers to Po and Qt file formats.Commits-------f05d4e4 [Translator] Set sources when extracting strings from php files