fix(transaction-pay-controller): use Infura endpoint for live token balance queries

[matthewwalsh0]

Explanation

When querying a live on-chain token balance, the controller previously resolved the network client using findNetworkClientIdByChainId, which returns whatever endpoint is currently selected for that chain — including custom RPC endpoints. Custom RPC endpoints may not support the pending block tag used by these calls, causing the query to fail.

This change adds a preference for the chain's Infura endpoint when one is configured, falling back to the existing findNetworkClientIdByChainId behaviour if no Infura endpoint is configured or if the lookup throws.

References

Checklist

• I've updated the test suite for new or updated code as appropriate
• I've updated documentation (JSDoc, Markdown, etc.) for new or updated code as appropriate
• I've communicated my changes to consumers by updating changelogs for packages I've changed
• I've introduced breaking changes in this PR and have prepared draft pull requests for clients and consumer packages to resolve them

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Note

Medium Risk
Changes which RPC endpoint serves balance validation and on-chain amount reads for pay/relay flows; behavior is mitigated by fallback to the default network client when Infura is missing.

Overview
Introduces shared getNetworkClientId / rpcRequest helpers that can prefer a chain’s Infura RPC (via NetworkController:getNetworkConfigurationByChainId) and otherwise fall back to the selected network client.

getLiveTokenBalance now uses direct JSON-RPC (eth_call / eth_getBalance with pending) through those helpers with preferInfura: true, replacing ethers Web3Provider/Contract—aimed at custom RPCs that don’t support pending block tags.

On-chain amount resolution for fiat flows and getTransferredAmountFromTxHash is updated to the same provider-based RPC path. Across, Relay submit, and gas estimation use getNetworkClientId without the Infura preference. Tests and the test messenger mock getNetworkConfigurationByChainId accordingly.

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