Remove "hash form" from alert management client-side router usage

Problem

Since #374724 (closed) we use the 🆕 "slash form" <base>/root/test-proj/-/alert_management/2/details/overview for tabs in alert details.

We also support the old "hash form" <base>/root/test-proj/-/alert_management/2/details#/overview so it redirects to the "slash form". See #374724 (comment 1143851220)

Long-term we want to only use "slash form" and remove "hash form".

Proposed solution

Remove support for "hash form".