Add more mainnet bootnodes

[manav2401]

Description

This PR updates mainnet bootnodes hardcoded in bor. Also, new-cli will now append the hardcoded nodes irrespective of what the user provides based on the network set (i.e. mainnet / mumbai).

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