…ator` using `_query` (BenMorel)

This PR was merged into the 7.4 branch.

Discussion
----------

[Routing] Allow query-specific parameters in `UrlGenerator` using `_query`

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

This PR adds support for a special `_query` key in `$parameters` of `UrlGenerator::generate()`, that is used exclusively to generate query parameters. This is useful when query parameters may conflict with route parameters of the same name.

Concrete use case:

My application has a route that looks like:

    https://{siteCode}.{domain}/admin/stats

And I want to generate this URL:

    https://fr.example.com/admin/stats?siteCode=us

With this PR, I can now call:

```php
$urlGenerator->generate('admin_stats', [
    'siteCode' => 'fr',
    'domain' => 'example.com',
    '_query' => [
        'siteCode' => 'us',
    ]
]);
```

Commits
-------

e3513bdf48c Allow query-specific parameters in URL generator using `_query`

* 7.4:
  Test AssetMapper with and without ext-brotli/ext-zstd in one job
  [PhpUnitBridge] Add `strtotime()` to `ClockMock`
  [JsonPath] Fix typo in comment in JsonCrawler
  Allow query-specific parameters in URL generator using `_query`