…per option (yceruto)

This PR was merged into the 5.1-dev branch.

Discussion
----------

[RFC][DX][OptionsResolver] Allow setting info message per option

| Q             | A
| ------------- | ---
| Branch?       | master
| Bug fix?      | no
| New feature?  | yes
| Deprecations? | no
| Tickets       | -
| License       | MIT
| Doc PR        | TODO

This is a DX proposal that will help in debugging/errors to better understand the meaning of one defined option.

This is how you'd use it:
```php
$resolver = new OptionsResolver();
$resolver->setDefined('date');
$resolver->setAllowedTypes('date', \DateTime::class);
$resolver->setInfo('date', 'A future date'); // <-- NEW
// ...
```
This information may be useful for those options where their name cannot be intuitive enough, or their purpose is too complex. Here is an example (based on the example above):
```php
// ...
$resolver->setAllowedValues('date', static function ($value): bool {
    return $value >= new \DateTime('now');
});
```
So, if you introduce a date value that does not match the criteria, you will get this error message:

**Before:**
```
The option "date" with value DateTime is invalid.
```
Note that the allowed value is not printable in this case, hence the error message cannot be clear at all.

**After:**
```
The option "date" with value DateTime is invalid. Info: A future date.
```
Although a more accurate error message can be triggered within the `\Closure` if desired.

Also you'll see this info message on `debug:form` command (see tests), then you have in advance the informative description of any option.

What do you think?

Commits
-------

0477a06 Allow setting one info message per option