fix(wallet): Re-Adds updateExchangeRates to setupOnChainWallet

[coreyphillips]

Description

• The latest version of beignet removed exchangeRates so this re-adds updateExchangeRates to the setupOnChainWallet method.
• Cleans up & Applies fix to lm.start function params so the electrum network is now read properly from beignet.
• Upgrades beignet to 0.0.20.

Type of change

• Bug fix (non-breaking change which fixes an issue)
• Refactoring (improving code without creating new functionality)

Tests

• No test

[pwltr]

Getting a warning every time the app starts:

 LOG  {"values": {"network": "regtest", "value": "exchangeRates", "walletName": "wallet0"}}
 ERROR  Error in setWalletData: [TypeError: Cannot convert undefined value to object]
 LOG  [TypeError: Cannot convert undefined value to object]