[Validator] Fix constraint violation message parameterization
[Validator] Fixed value-to-string conversion in constraint violations
[Validator] Simplified IBAN validation algorithm
[Validator] Fixed and simplified IsbnValidator
[Validator] Simplified IssnValidator
[Validator] Simplified and explained the LuhnValidator
[Validator] Added "{{ value }}" parameters where they were missing
[Validator] Fixed date-to-string conversion tests to match ICU 51
[Validator] Fixed CS
[Validator] Renamed valueToString() to formatValue(); added missing formatValue() calls
properly handle null data when denormalizing

If null is passed to denormalize(), no property values can be set on
the denormalized object. Additionally, this fixes passing values to
the denormalized object's constructor if the incoming data is an object.
[Validator] Removed information from the violation output if the value is an array, object or resource

This was decided in the discussion of #10687.
[Validator] Added more detailed inline documentation
bug #10687 [Validator] Fixed string conversion in constraint violations (eagleoneraptor, webmozart)

This PR was merged into the 2.3 branch.

Discussion
----------

[Validator] Fixed string conversion in constraint violations

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | #10675
| License       | MIT
| Doc PR        | -

Commits
-------

32ae95b [Validator] Added more detailed inline documentation
08ea6d3 [Validator] Removed information from the violation output if the value is an array, object or resource
d6a783f [Validator] Renamed valueToString() to formatValue(); added missing formatValue() calls
71897d7 [Validator] Fixed CS
cea4155 [Validator] Fixed date-to-string conversion tests to match ICU 51
5aa7e6d [Validator] Added "{{ value }}" parameters where they were missing
f329552 [Validator] Simplified and explained the LuhnValidator
bff09f2 [Validator] Simplified IssnValidator
224e70f [Validator] Fixed and simplified IsbnValidator
fd58870 [Validator] Simplified IBAN validation algorithm
97243bc [Validator] Fixed value-to-string conversion in constraint violations
75e8815 [Validator] Fix constraint violation message parameterization
[Console] Roll back changes made to fixture files.

Original change was made in e9022adaef40330a92bdf0916bf0b995f942c7fa.
[DependencyInjection] Roll back changes made to generated files.

Original change was made in e9022adaef40330a92bdf0916bf0b995f942c7fa.
bug #11428 [Serializer] properly handle null data when denormalizing (xabbuh)

This PR was merged into the 2.3 branch.

Discussion
----------

[Serializer] properly handle null data when denormalizing

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | #10794
| License       | MIT
| Doc PR        |

Commits
-------

123fc62 properly handle null data when denormalizing
minor #11537 Make builds green again (jakzal)

This PR was merged into the 2.3 branch.

Discussion
----------

Make builds green again

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | -
| License       | MIT
| Doc PR        | -

This PR rolls back changes made to the fixture and generated files in e9022adaef40330a92bdf0916bf0b995f942c7fa (#11512).

Commits
-------

88b4e70 [DependencyInjection] Roll back changes made to generated files.
f89811d [Console] Roll back changes made to fixture files.
[Process] Fix tests when pcntl is not available.
minor #11539 [Process] Fix tests when pcntl is not available. (jakzal)

This PR was merged into the 2.3 branch.

Discussion
----------

[Process] Fix tests when pcntl is not available.

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | -
| License       | MIT
| Doc PR        | -

It's solved the same way in the [AbstractProcessTest](https://github.com/symfony/symfony/blob/3b837dc5c102b8210b7038029416c0524d5f458b/src/Symfony/Component/Process/Tests/AbstractProcessTest.php#L602-L603).

Commits
-------

e40f24f [Process] Fix tests when pcntl is not available.