Replace the current toolbar implementation with the new PageHeader component on the (rails) global index pages

* [x] Homepage
* [x] Activity
* [x] Calendar (index page)
* [x] Boards (index page)
* [x] Team planner (index page)
* [x] News
* [x] Time and costs

# QA

* Begin of the insertion[x]End of the insertion Begin of the deletion [ ]End of the deletion On the homepage:
* Begin of the insertion[x]End of the insertion Begin of the deletion [ ]End of the deletion the old header is still shown.
* Begin of the insertion[x]End of the insertion Begin of the deletion [ ]End of the deletion Instead of "Home", I think the name of the instance should be shown

<img class="image_resized op-uc-image op-uc-image_inline" style="width:318px;" src="/api/v3/attachments/199624/content">

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* Begin of the insertion[x]End of the insertion Begin of the deletion [ ]End of the deletion In meetings:
* Begin of the insertion[x]End of the insertion Begin of the deletion [ ]End of the deletion The breadcrumb says &quot;Home -&gt; Meetings&quot;, while all other have &quot;_Instance name_ -&gt; _Module name_&quot;

<img class="image_resized op-uc-image op-uc-image_inline" style="width:286px;" src="/api/v3/attachments/199625/content">

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* Begin of the insertion[x]End of the insertion Begin of the deletion [ ]End of the deletion Time and costs is completely weird:
* Begin of the insertion[x]End of the insertion Begin of the deletion [ ]End of the deletion The current element shows &quot;News&quot;, instead of &quot;Time and costs&quot;
* [ ] ~~The name of the current saved view is missing,~~ see <mention class="mention" data-id="58358" data-type="work_package" data-text="#58358">#58358</mention>&nbsp;

<img class="image_resized op-uc-image op-uc-image_inline" style="width:356px;" src="/api/v3/attachments/199626/content">

* Begin of the insertion[x]End of the insertion Begin of the deletion [ ]End of the deletion All pages with a create button (e.g. Boards, team planner, Calendar)
* Begin of the insertion[x]End of the insertion Begin of the deletion [ ]End of the deletion The button is not a Primer button

<img class="image_resized op-uc-image op-uc-image_inline" style="width:166px;" src="/api/v3/attachments/199627/content">