[Feature Request] Add expand/collapse all button to the suites tree

**Background**
When opening an Allure 3 report, the suites tree loads with previously expanded state preserved — and applying a status filter (e.g. failed, passed) causes all matching suites to expand automatically. With a large number of suites, this quickly becomes difficult to navigate: finding a specific suite or test requires manually collapsing many nodes one by one.

**Proposal**
Add an "expand all / collapse all" toggle button to the suites tree toolbar, ideally alongside the existing sort controls. This would let users quickly reset the tree to a collapsed state and navigate from there.

**Workarounds considered**
Wrapping all suites under a single top-level suite — this adds an extra nesting level and doesn't fully solve the problem, since expanding any lower-level suite re-expands its children as well.
Manually collapsing each suite — tedious at scale.

Neither is a satisfying substitute for a proper collapse-all control.

Start by locating the suites tree toolbar and its existing sort controls in the report UI. Add an expand-all/collapse-all toggle that lets users reset the tree to a collapsed state, then verify it works with large trees and status-filtered suites.

Written by the indexing model from the issue text.