Optimize fetching of blockchain data and update package-lock for node LTS

[zquestz]

This PR cleans up quite a few things.

1. Update package-lock to work with latest Node LTS (v16).
2. Optimizes fetching of blocks/addresses/transactions so they are only fetched once. SearchBCHD() was called multiple times in the old code path.
3. Adds debug method which can be used to log to console.
4. Ran main BCHDExplorer.vue through a JS formatter.
5. Updated polling interval for basic blockchain info to 60 seconds (from 5 seconds).
6. Simplifies testnet detection.