fix: remove duplicate POL tokens from swap select token screen

[GeorgeGkas]

Description

POL token is defined with zero address in our backend services but its actual address is 0x0000000000000000000000000000000000001010. That creates an issue where both tokes are rendered even if they are the same. To mitigate this issue we keep the one with zero address as it's more consistent with similar logic.

Changelog

CHANGELOG entry: Fixes an issue where users will see two POL tokens on swap select token screen

Related issues

Fixes: #19334

Manual testing steps

- Ensure that users see only one POL token on Select Token screen of swaps.
- Ensure that POL token rendered in Select Token screen of swaps have correct balance.
- Ensure that users can complete a swap or bridge transaction using POL token both as source and dest.

Screenshots/Recordings

Before

After

Pre-merge author checklist

• I’ve followed MetaMask Contributor Docs and MetaMask Mobile Coding Standards.
• I've completed the PR template to the best of my ability
• I’ve included tests if applicable
• I’ve documented my code using JSDoc format if applicable
• I’ve applied the right labels on the PR (see labeling guidelines). Not required for external contributors.

Pre-merge reviewer checklist

• I've manually tested the PR (e.g. pull and build branch, run the app, test code being changed).
• I confirm that this PR addresses all acceptance criteria described in the ticket it closes and includes the necessary testing evidence such as recordings and or screenshots.

---

Note

Normalize Polygon native token addressing to dedupe POL across token sources and ensure correct rendering/exclusion.

• Bridge tokens:
  • Normalize Polygon native token by mapping 0x0000000000000000000000000000000000001010 to zeroAddress() in useTokens getTokenKey for consistent deduplication across sources.
  • Respect exclusions for POL regardless of whether specified as zeroAddress() or native address.
• Tests:
  • Add comprehensive tests in hooks/useTokens.test.ts covering:
    • Duplicate prevention between tokensWithBalance and topTokens (both address variants).
    • Mixed-chain behavior (ETH unaffected), allTokens normalization, and exclusion cases.
• Constants:
  • Introduce POLYGON_NATIVE_TOKEN in constants/assets.ts.

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[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
100.0% Coverage on New Code
0.0% Duplication on New Code

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