…ct()` (jwage)

This PR was squashed before being merged into the 6.4 branch.

Discussion
----------

[Messenger] Improve deadlock handling on `ack()` and `reject()`

| Q             | A
| ------------- | ---
| Branch?       | 6.4
| Bug fix?      | yes
| New feature?  | no
| Deprecations? | no
| Issues        | Fix #54103
| License       | MIT

We started getting this deadlock recently. It has happened only twice so far under high load.

```
SQLSTATE[40P01]: Deadlock detected: 7 ERROR:  deadlock detected
DETAIL:  Process 221664 waits for ShareLock on transaction 59539641; blocked by process 221671.
Process 221671 waits for AccessExclusiveLock on tuple (77,27) of relation 16455 of database 16385; blocked by process 221605.
Process 221605 waits for ShareLock on transaction 59539646; blocked by process 221606.
Process 221606 waits for AccessExclusiveLock on tuple (69,16) of relation 16455 of database 16385; blocked by process 221664.
HINT:  See server log for query details.
CONTEXT:  while deleting tuple (69,16) in relation "messenger_messages"
Process 221664 waits for ShareLock on transaction 59539641;
blocked by process 221671.
```

Here are the queries for each process:

```
Process 221664 waits for ShareLock on transaction 59539641;
blocked by process 221671.

221671
SELECT m.* FROM messenger_messages m WHERE (m.queue_name = $1) AND (m.delivered_at is null OR m.delivered_at < $2) AND (m.available_at <= $3) ORDER BY available_at ASC LIMIT 1 FOR UPDATE

221605
SELECT m.* FROM messenger_messages m WHERE (m.queue_name = $1) AND (m.delivered_at is null OR m.delivered_at < $2) AND (m.available_at <= $3) ORDER BY available_at ASC LIMIT 1 FOR UPDATE

221606
SELECT m.* FROM messenger_messages m WHERE (m.queue_name = $1) AND (m.delivered_at is null OR m.delivered_at < $2) AND (m.available_at <= $3) ORDER BY available_at ASC LIMIT 1 FOR UPDATE

221664
DELETE FROM messenger_messages WHERE id = $1
```

Open for discussion if this is the right way to handle this or not.

TODO:

- [x] Should there be a retry delay/exponential backoff/jitter? Retrying the failed delete that deadlocked immediately may not help.
- [x] Should `skip_locked` even be an option or should we always use skip locked?
- [x] Should we add `SKIP LOCKED` to the `FOR UPDATE`? It will reduce contention further. I was looking at how SolidQueue in Ruby On Rails handles this and it appears they use `SKIP LOCKED FOR UPDATE` https://github.com/basecamp/solid_queue/blob/fe57349a126efc381fe0adf4c1ec444bd8a4f53f/app/models/solid_queue/record.rb#L11

Commits
-------

38b67e7d7f [Messenger] Improve deadlock handling on `ack()` and `reject()`

* 6.4:
  fix merge
  fix syntax for PHP 7.2
  [Security] Fix Danish translations
  [Messenger] Improve deadlock handling on `ack()` and `reject()`
  [DomCrawler] Encode html entities only if nessecary
  [Serializer] reset backed_enum priority, and re-prioritise translatable
  [Validator] Accept `Stringable` in `ExecutionContext::build/addViolation()`
  [Serializer] Ignore when using #[Ignore] on a non-accessor
  [Filesystem] Strengthen the check of file permissions in `dumpFile`
  [Serializer] Fix XML scalar to object denormalization
  [HttpClient][EventSourceHttpClient] Fix consuming SSEs with \r\n separator

* 6.4:
  initialize the current time with midnight before modifying the date
  fix tests
  [HtmlSanitizer] Ignore Processing Instructions

* 5.4:
  explicitly mark nullable parameters as nullable
  fix low deps tests
  [HttpKernel] Fix datacollector caster for reference object property
  bug #51578 [Cache] always select database for persistent redis connections
  [Security] Validate that CSRF token in form login is string similar to username/password
  [validator] validated Dutch translation
  Improve dutch translations
  [Translation] Skip state=needs-translation entries only when source == target
  [HttpKernel] Ensure controllers are not lazy
  [Validator] Fill in trans-unit id 113: This URL does not contain a TLD.
  [Validator] added missing Polish translation for unit 113
  [Validator] add missing lv translation
  [HttpClient] Let curl handle transfer encoding
  [Messenger] Make Doctrine connection ignore unrelated tables on setup
  [HttpFoundation] Set content-type header in RedirectResponse
  add translations for the requireTld constraint option message
  [Serializer] Fix unexpected allowed attributes
  [FrameworkBundle] Fix registration of the bundle path to translation

* 6.4: (23 commits)
  fix merge
  add missing return type-hints
  fix merge
  explicitly mark nullable parameters as nullable
  fix low deps tests
  [HttpKernel] Fix datacollector caster for reference object property
  [Serializer] Fixing PHP warning in the ObjectNormalizer with MaxDepth enabled
  bug #51578 [Cache] always select database for persistent redis connections
  [Security] Validate that CSRF token in form login is string similar to username/password
  [Serializer] Use explicit nullable type
  [validator] validated Dutch translation
  Improve dutch translations
  [Translation] Skip state=needs-translation entries only when source == target
  [HttpKernel] Ensure controllers are not lazy
  [Validator] Fill in trans-unit id 113: This URL does not contain a TLD.
  [Validator] added missing Polish translation for unit 113
  [Validator] add missing lv translation
  [HttpClient] Let curl handle transfer encoding
  [Messenger] Make Doctrine connection ignore unrelated tables on setup
  [HttpFoundation] Set content-type header in RedirectResponse
  ...

* 5.4:
  Auto-close PRs on subtree-splits
  review German translation

* 6.4:
  Auto-close PRs on subtree-splits
  review German translation