Fix #8529: Update logic to support unknown tokens from non-mainnet transactions

[StephenHeaps]

Summary of Changes

• Previously we relied on the GetTokenInfo api on Asset Ratio Service to fetch tokens, but this api was ethereum mainnet only. By using GetEthTokenDecimals and GetEthTokenSymbol we can use RPC to fetch tokens from non-mainnet ethereum networks, for example Goerli.
• Added a GetEthTokenInfo api extension to JsonRpcService. This API can/will be replaced in a future version of BraveCore: https://github.com/brave/brave-core/pull/21191

This pull request fixes #8529

Submitter Checklist:

• [x] Unit Tests are updated to cover new or changed functionality
• [x] User-facing strings use NSLocalizableString()
• [x] New or updated UI has been tested across:
  • [x] Light & dark mode
  • [x] Different size classes (iPhone, landscape, iPad)
  • [x] Different dynamic type sizes

Test Plan:

1. Create a non-mainnet Ethereum transaction for a token not in user assets or blockchain registry (asset search in wallet).
   • I used cow swap to swap ETH to CoW token on Goerli Test network for testing.
   • https://swap.cow.fi/#/5/swap/ETH/COW
2. Verify token symbol and transaction value shows up as expect in Swap Confirmation, Activity tab, Tx details, etc.

Screenshots:

Reviewer Checklist:

• [ ] Issues include necessary QA labels:
  • QA/(Yes|No)
  • bug / enhancement
• [ ] Necessary security reviews have taken place.
• [ ] Adequate unit test coverage exists to prevent regressions.
• [ ] Adequate test plan exists for QA to validate (if applicable).
• [ ] Issue and pull request is assigned to a milestone (should happen at merge time).