Implement gRPC bidirectional communication between heimdall and bor

[marcello33]

Description

With this PR, we enable the bidirectional communication of heimdall and bor via gRPC protocol.

Changes

• Bugfix (non-breaking change that solves an issue)
• Hotfix (change that solves an urgent issue, and requires immediate attention)
• New feature (non-breaking change that adds functionality)
• Breaking change (change that is not backwards-compatible and/or changes current functionality)
• Changes only for a subset of nodes

Checklist

• I have added at least 2 reviewer or the whole pos-v1 team
• I have added sufficient documentation in code
• I will be resolving comments - if any - by pushing each fix in a separate commit and linking the commit hash in the comment reply

Cross repository changes

• This PR requires changes to bor
  • In case link the PR here: Implement gRPC bidirectional communication between bor and heimdall bor#1373
• This PR requires changes to matic-cli
  • In case link the PR here: Enable gRPC in heimdall config and install tools to test it remotely matic-cli#256

Testing

• I have added unit tests
• I have added tests to CI
• I have tested this code manually on local environment
• I have tested this code manually on remote devnet using express-cli
• I have tested this code manually on mumbai or amoy
• I have created new e2e tests into express-cli