Adjust schedule view time frame
### Release notes
### Problem to solve
In https://gitlab.com/gitlab-org/gitlab/-/issues/262848, we are creating a static schedule. We will need to introduce a way for people to change the dates being displayed.
### Intended users
* [Devon (DevOps Engineer)](https://about.gitlab.com/handbook/marketing/product-marketing/roles-personas/#devon-devops-engineer)
* [Allison (Application Ops)](https://about.gitlab.com/handbook/marketing/product-marketing/roles-personas/#allison-application-ops)
* [Priyanka (Platform Engineer)](https://about.gitlab.com/handbook/marketing/product-marketing/roles-personas/#priyanka-platform-engineer)
### User experience goal
Allow users to easily adjust the view of their schedules so that they can see who is on-call in upcoming days/weeks/months.
### Proposal
For a first iteration, we will add forward/backward buttons to the schedule view:

For a first pass, clicking the forward or backward button will shift the schedule forward or backward in two week increments.
[Figma file](https://www.figma.com/file/gZF7Vvj1mmZGZFkV9wXTpY/Design-discovery-on-call-scheduling-gitlab-com-and-25995?node-id=364%3A2009)
### Further details
This work supports the [Incident management](https://about.gitlab.com/direction/monitor/debugging_and_health/incident_management/) direction.
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### Is this a cross-stage feature?
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issue
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