IPLD Block Explorer should work with multiple watchers

[stellarmagnet]

At the moment, the IPLD Block Explorer is just relying on a single watcher, eth-watcher-ts

But this watcher does not have all of the functionality required to build out the missing pages such as:

• Token list - https://www.ethvm.com/tokens
• Token landing page with transfers and holders list- https://www.ethvm.com/token/0x1f9840a85d5af5bf1d1762f925bdaddc4201f984
• Address landing page - https://www.ethvm.com/address/0xa090e606e30bd747d4e6245a1517ebe430f0057e

There are different watchers being developed by @ashwinphatak now, that we are going to have to consume to build the above pages.

To move in the direction of consuming these watchers, a new explorer-watcher-ts "parent" watcher should be created, which then is consuming child watchers such as eth-watcher-ts, erc20-watcher, address-watcher, etc.

The purpose of this epic is to re-architect the system as necessary to begin consuming both eth-watcher-ts and erc20-watcher in an elegant manner, with the goal that in future sprints we can integrate with additional watchers as they are completed (such as address watcher).

Acceptance criteria

• IPLD Block Explorer can work with multiple watchers in an elegant manner
• IPLD Block Explorer is integrated with eth-watcher-ts using the multi-watcher design
• IPLD Block Explorer is integrated with erc20-watcher using the multi-watcher design

[ramilexe]

1. Not sure I understand how "parent" watcher explorer-watcher-ts will interact with child watchers. Will it have its own database and pull all data from the child's database to its local? Or just proxy graphql requests?
2. I tried to run erc20-watcher, followed the instruction in README and after I ran it get errors:

  vulcanize:events Started watching upstream logs... +0ms
  vulcanize:server Starting server... +0ms
  vulcanize:server Server is listening on host 127.0.0.1 port 3001 +2ms
  vulcanize:eth-client Subscription client error connect ECONNREFUSED 127.0.0.1:5000 +0ms
  vulcanize:eth-client Subscription client error connect ECONNREFUSED 127.0.0.1:5000 +151ms
  vulcanize:eth-client Subscription client error connect ECONNREFUSED 127.0.0.1:5000 +235ms
  vulcanize:eth-client Subscription client error connect ECONNREFUSED 127.0.0.1:5000 +590ms
  vulcanize:eth-client Subscription client error connect ECONNREFUSED 127.0.0.1:5000 +945ms
  vulcanize:eth-client Subscription client error connect ECONNREFUSED 127.0.0.1:5000 +922ms

what is expected to be running on port 5000? Am I missing something in instruction?
3. How to get Token list like this https://www.ethvm.com/tokens from watcher-ts?
4. How to get basic erc20 token information in case storage layout will be different than default?
5. How to get Transfers and Holders information by token?
6. Hot to get Total ERC20 Tokens and Transaction History by address?