Refactor: extract shared governance logic into governance-helpers crate

[NachoPal]

Overview

• Extracts duplicated governance flow (Council → TC → FederatedAuthority) from util/upgrader and util/toolkit/commands/root_call.rs into a new shared util/governance-helpers crate
• Both the upgrader and toolkit now delegate to governance_helpers::execute_governance_call() instead of maintaining their own copies of the voting/proposal logic
• Adds governance_helpers=info to the toolkit's default log filter so governance step logs remain visible

#1189

🗹 TODO before merging

• Ready

📌 Submission Checklist

• Changes are backward-compatible (or flagged if breaking)
• Pull request description explains why the change is needed
• Self-reviewed the diff
• I have included a change file, or skipped for this reason:
• If the changes introduce a new feature, I have bumped the node minor version
• Update documentation (if relevant)
• Updated AGENTS.md if build commands, architecture, or workflows changed
• No new todos introduced

🧪 Testing Evidence

Please describe any additional testing aside from CI:

• Additional tests are provided (if possible)

🔱 Fork Strategy

• Node Runtime Update
• Node Client Update
• Other:
• N/A

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