FE: Add rule humanization support for `branch_type`

Summary

We are adding branch_type support to security policies.

The policy editor sidebar drawer needs to support humanizing policy rules that use branch_types instead of branches.

Currently, for any policy that uses branch_types rules, the sidebar displays "No rules defined - policy will not run":

Implementation Plan

A proof-of-concept can be found on the 9468-branch-expressions branch.

• frontend Change humanize.js so that branch_type rules are spelled out correctly for scan execution policies
• frontend Change humanize.js so that branch_type rules are spelled out correctly for scan result policies