Exporting formatIconUrlWithProxy to format iconUrl Proxy for tokens from swaps api

[NiranjanaBinoy]

We need to use formatIconUrlWithProxy in extension for formating the token iconURL to proxy for the tokens from swap API. Since the extension is currently using a static token list for the scenario when token detection is OFF on MAINNET, we cannot use the proxy iconUrl from the dynamic token list as the default one for swap.