Automatically add new token to wallet's token list

**What problem are you trying to solve?**
Improve UX and onboarding when a wallet is imported or when a new ERC20 token is received

**Describe the solution you'd like**
Metamask should check a wallet's incoming transactions when it is imported and thereafter to detect when a new ERC20 token is received and add the token to the wallet's token list. At first, possibly only include tokens that are searchable from the Metamask UI (i.e. tokens within eth-contract-metadata/contract-map.json)

**Additional context**
support reference: 32887

Start by reviewing the wallet import flow, incoming transaction handling, and eth-contract-metadata/contract-map.json mentioned in the issue. Define how detection runs on import and thereafter, and verify that newly received searchable ERC20 tokens appear in the wallet's token list without manual setup.

Written by the indexing model from the issue text.