System dashboard: Buttons are missing keyboard support.

Steps to reproduce:

1. Navigate to and activate "Dashboards> View system dashboard" from the banner region.
2. Using keyboard, navigate to the "Full view", "List view" buttons present under "Activity Stream" section.

Screenshot:

Actual behaviour:

While keyboard users navigate the page using Tab key, the "Full view", "List view" buttons do not receive keyboard focus. In addition, for screen reader users, these interactive elements may appear as plain text elements and thus they may not be able to use the functionality related to these buttons.

Expected result:

1. The <span> element should be replaced with native <button> element and logical label should be provided using "aria-label" attribute. This will ensure accurate role and label to be announced for screen reader users and the element will receive keyboard focus too due to element’s native behaviour.
2. aria-pressed should be provided to the button elements and its value should be programmatically controlled true / false depending on the activated state of button. This will ensure announcement for state of buttons for screen reader users.

AXQA Ref:AXQA-92