feat(perps): remove USDH collateral handling from HyperLiquid provider

[michalconsensys]

Description

Removes all USDH collateral handling logic from the HyperLiquid provider. USDH support is being sunset, so the automatic USDC→USDH swap flow, spot balance checks, and session-cached spot metadata are no longer needed.

Changes

• Removed USDH_CONFIG constant and its public export
• Removed private methods: #isUsdhCollateralDex, #getSpotUsdhBalance, #getSpotUsdcBalance, #transferUsdcToSpot, #swapUsdcToUsdh, #ensureUsdhCollateralForOrder, #getCachedSpotMeta
• Removed #cachedSpotMeta field and its pre-fetch in ensureReadyForTrading()
• Removed USDH collateral branch from #ensureCollateralForHip3Order
• Simplified #getUsdcTokenId to call spotMeta() directly instead of going through the removed cache
• Removed unused imports (SPOT_ASSET_ID_OFFSET, SpotMetaResponse)
• Updated tests to use generic non-USDC tokens (HYPE, PURR) instead of USDH

Changelog

@metamask/perps-controller

• Removed: USDH collateral handling — spot balance checks, USDC→USDH swaps, and USDH_CONFIG constant

Related issues

N/A

Manual testing steps

N/A — internal cleanup with no behavioral change for USDC-collateralized DEXs.

Screenshots/Recordings

N/A

Pre-merge author checklist

• I've followed MetaMask Contributor Docs
• 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
• I've properly set the pull request to draft if not ready to be reviewed

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 parties involved