Remove redundant method from Route interface

[artursapek]

isProtocolSupported is redundant with supportedChains. We should keep the Route interface as small as possible to make it easy for plugins to be written. This reduces the interface to four consistent methods, which I think is cleaner:

  supportedNetworks(): Network[];

  supportedChains(network: Network): Chain[];

  supportedSourceTokens(fromChain: ChainContext<Network>): Promise<TokenId[]>;

  supportedDestinationTokens<N extends Network>(
    token: TokenId,
    fromChain: ChainContext<N>,
    toChain: ChainContext<N>,
  ): Promise<TokenId[]>;