feat(api): add support for witnetPriceFeeds contract

Add support for networks using [WitnetFeeds contract](https://github.com/witnet/witnet-solidity-bridge/blob/2.0.x/contracts/apps/WitnetFeeds.sol):
- Implement the NetworkRouter class that handles all the communication with each network.
- Listen to the networks using the `WitnetPriceRouter` with `listenLegacyPriceRouter` and the new network using `WitnetFeeds` with `listenWitnetPriceFeeds`.
- Update the configuration file. The networks still using the old witnet price router are marked using `legacy: true` in the network configuration. Also, the file configuration has been updated to include the feed key. This new key consists of a map with the default values of the existing price feeds. According to that, the price feeds deployed using the default configuration have been deleted from the network feeds section. If a feed configuration appears in the network feeds, it will overwrite the default configuration. Now, we get all the available price feeds in a network called the [supportedFeeds](https://github.com/witnet/witnet-solidity-bridge/blob/2.0.x/contracts/interfaces/IFeeds.sol#L8) method.

packages/api/jest.config.js

@@ -1,4 +1,4 @@
-require('dotenv/config')
+// require('dotenv/config')
 
 module.exports = {
   preset: 'ts-jest',

packages/api/package.json

@@ -35,13 +35,14 @@
     "axios": "^1.3.6",
     "dataloader": "2.2.2",
     "dotenv": "^16.0.3",
+    "graphql": "^15.5.0",
     "graphql-tag": "^2.12.6",
     "jest": "^29.5.0",
     "migrate-mongo": "^8.2.3",
     "mongodb": "4.16.0",
     "node-cache": "^5.1.2",
     "web3": "^1.9.0",
-    "web3-utils": "^1.9.0",
-    "graphql": "^15.5.0"
+    "web3-eth-contract": "^1.10.0",
+    "web3-utils": "^1.9.0"
   }
 }