* 3.4:
  [Cache] fix memory leak when using PhpArrayAdapter
  fix parsing negative octal numbers
  [SecurityBundle] Properly escape regex in AddSessionDomainConstraintPass
  [Config] never try loading failed classes twice with ClassExistenceResource

* 4.3:
  gracefully handle missing event dispatchers
  [Cache] fix memory leak when using PhpArrayAdapter
  fix parsing negative octal numbers
  [SecurityBundle] Properly escape regex in AddSessionDomainConstraintPass
  [Config] never try loading failed classes twice with ClassExistenceResource

…ed values (natepage)

This PR was squashed before being merged into the 3.4 branch.

Discussion
----------

[Yaml] Implement multiline string as scalar block for tagged values

| Q             | A
| ------------- | ---
| Branch?       | 3.4
| Bug fix?      | yes
| New feature?  | no <!-- please update src/**/CHANGELOG.md files -->
| Deprecations? | no <!-- please update UPGRADE-*.md and src/**/CHANGELOG.md files -->
| Tickets       | Fix #... <!-- prefix each issue number with "Fix #", if any -->
| License       | MIT

At the moment you can parse a tagged value defined as a scalar block. But you can't actually dump a multiline string as scalar block when using a tagged value.

This PR implements the multiline string as scalar block for tagged values as well.

Commits
-------

84241d4e62 [Yaml] Implement multiline string as scalar block for tagged values

* 3.4:
  [Yaml] Implement multiline string as scalar block for tagged values
  [HttpFoundation] Use `Cache-Control: must-revalidate` only if explicit lifetime has been given
  [FrameworkBundle] Use UserInterface to @return in getUser method
  [CI] Replace php7.4snapshot with php7.4 in Travis configuration
  [ExpressionLanguage][Node][BinaryNode] Process division by zero
  forward caught exception
  [Validator][ConstraintValidator] Stop passing unnecessary timezone argument to \DateTime
  add tags before processing them
  [MonologBridge] Fix debug processor datetime type

* 4.3:
  [Cache] fix memory leak when using PhpFilesAdapter
  [Yaml] Implement multiline string as scalar block for tagged values
  [HttpFoundation] Use `Cache-Control: must-revalidate` only if explicit lifetime has been given
  [FrameworkBundle] Use UserInterface to @return in getUser method
  [CI] Replace php7.4snapshot with php7.4 in Travis configuration
  [ExpressionLanguage][Node][BinaryNode] Process division by zero
  forward caught exception
  [Validator][ConstraintValidator] Stop passing unnecessary timezone argument to \DateTime
  add tags before processing them
  [MonologBridge] Fix debug processor datetime type