OP Superchain explorer: aggregated views

[tom2drum]

Description and Related Issue(s)

This is the final part of the multichain explorer development, which began in #2786 and continued in #2864. It resolves issues #2989 and #2879.

Proposed Changes

• Finalize and document the following environment variables for the multichain explorer:
  • NEXT_PUBLIC_MULTICHAIN_ENABLED: the flag that enables the feature
  • NEXT_PUBLIC_MULTICHAIN_CLUSTER: the chain's cluster name
  • NEXT_PUBLIC_MULTICHAIN_AGGREGATOR_API_HOST: the multichain aggregator API service host
  • NEXT_PUBLIC_MULTICHAIN_STATS_API_HOST: the multichain statistics API service host
• Eliminate the need for all standard environment variables for the usual explorer in the multichain explorer. Introduce a separate environment validation schema for the multichain explorer.
• Refactor the ChainIndicator component on the main page to reuse its parts.
• Add a search bar button on the search results page.

Additional Information

This feature is currently in demo mode. A significant portion of the cross-chain views is not yet implemented and serves as a placeholder. These will be developed in the future.

Checklist for PR author

• I have tested these changes locally.
• I added tests to cover any new functionality, following this guide
• Whenever I fix a bug, I include a regression test to ensure that the bug does not reappear silently.
• If I have added, changed, renamed, or removed an environment variable
  • I updated the list of environment variables in the documentation
  • I made the necessary changes to the validator script according to the guide
  • I added "ENVs" label to this pull request