feature #61718 [Config] Add argument $singular to NodeBuilder::arrayNode() to decouple plurals/singulars from XML (nicolas-grekas)

This PR was merged into the 7.4 branch.

Discussion
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[Config] Add argument `$singular` to `NodeBuilder::arrayNode()` to decouple plurals/singulars from XML

| Q             | A
| ------------- | ---
| Branch?       | 7.4
| Bug fix?      | no
| New feature?  | yes
| Deprecations? | no
| Issues        | -
| License       | MIT

The capability of defining plural/singular variants for config node is used not only for XML but also for config builders generation.

The current method to deal with this concern is named `fixXmlConfig()`. It's confusing to say the least. What's also confusing is that the call needs to happen on the parent node.

This PR proposes to add a second argument to the `arrayNode()` method, so that things could be changed like this (example taken from the attached patch):

```diff
        $rootNode
-           ->fixXmlConfig('role', 'role_hierarchy')
            ->children()
-               ->arrayNode('role_hierarchy')
+               ->arrayNode('role_hierarchy', 'role')
```

I'm not deprecating the `fixXmlConfig()` method - it would be way too early.

~In a follow up PR, I'll try to require setting this second argument (or calling fixXmlConfig) when a prototype is defined. If possible.~

Commits
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5ac6e748eb9 [Config] Add argument $singular to NodeBuilder::arrayNode() to decouple plurals/singulars from XML

Author: fabpot