bug #16023 Minor fixes for the profiler and toolbar (javiereguiluz)

This PR was squashed before being merged into the 2.8 branch (closes #16023).

Discussion
----------

Minor fixes for the profiler and toolbar

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | partially #15439
| License       | MIT
| Doc PR        | -

Changes:

  * Fixed a misaligned icon
  * Changed the priorities of the collectors to better control their position and to leave a "gap" between priorities so custom panels can be displayed between the default panels. This idea came from @stof.

By the way, @stof do you know how can I set the priority of the SwiftMailer collector? Its definition is the only one that doesn't use the `<tag name="data_collector" />`:

```xml
<service id="swiftmailer.data_collector" class="%swiftmailer.data_collector.class%">
    <argument type="service" id="service_container" />
</service>
```

https://github.com/symfony/swiftmailer-bundle/blob/master/Resources/config/swiftmailer.xml#L90-L92

Commits
-------

bff4098 Minor fixes for the profiler and toolbar

Author: fabpot

Resources/config/collectors.xml

@@ -10,7 +10,7 @@
 
     <services>
         <service id="data_collector.security" class="%data_collector.security.class%" public="false">
-            <tag name="data_collector" template="@Security/Collector/security.html.twig" id="security" />
+            <tag name="data_collector" template="@Security/Collector/security.html.twig" id="security" priority="270" />
             <argument type="service" id="security.token_storage" on-invalid="ignore" />
             <argument type="service" id="security.role_hierarchy" />
             <argument type="service" id="security.logout_url_generator" />