Move Product Analytics to Beta

Overview

Once PA is ready for beta, we need to remove the restrictions on the feature and allow any Ultimate SaaS user to opt-in.

• Dependent on Add Product Analytics to Experiment features list (#414865 - closed)

Implementation Plan

• Update documentation from Experiment to Beta.
• Remove feature flags from the codebase.
  • The only toggle that should prevent users from using PA is the namespace-level Experiment Features flag which any namespace owner can toggle.