refactor(solana-wallet-snap): remove asset pubkeys

[ulissesferreira]

Summary

• Remove pubkey from the Solana TokenAsset and NftAsset models.
• Stop copying token account pubkeys into persisted or monitored asset entities.
• Resolve the associated token account address only when fetching transaction history, using the mint token program so Token-2022 remains supported.
• Keep independent account, metadata, saved-history, ATA-resolution, and transaction requests parallel where applicable.

Validation

• Formatting check passed.
• ESLint passed for all changed source and test files.
• Focused Jest execution was blocked because this worktree does not have a built packages/solana-wallet-snap/dist/bundle.js; the local build is also blocked by the current workspace package-resolution state for @metamask/snap-networks-utils.

This PR is based on the latest origin/main.