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. The implementation looks up the network configuration for the chain and selects the first `RpcEndpointType.Infura` endpoint it finds, 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