Add Brave Wallet to WATCH_ASSET_SUPPORED_WALLETS array

[coderabbitai]

Description

Brave Wallet supports wallet_watchAsset per EIP-747. The WATCH_ASSET_SUPPORED_WALLETS array in libs/wallet/src/constants.ts currently only includes METAMASK_RDNS but should also include BRAVE_WALLET_RDNS.

There is a TODO comment in libs/wallet/src/api/hooks.ts:95 noting this work needs to be done.

Context

This was flagged during review of PR #6619 but marked as out of scope for that PR.

Related PR: #6619
Review Comment: #6619 (comment)
Requested by: @kernelwhisperer