Fix/rate limit 1157

[Torresmorah]

Decrease the number of requests in the main page.

What does this PR do?

• Resolve Rate limit exceeded error #1157
• Fix error that ignores the given interval and requests the information of a block more times than necessary.
• When all endpoints fail, it stops requesting data and waits 30 seconds until an endpoint responds.
• Add ultra testnet endpoints to avoid data loss.

Steps to test

1. Run the project locally.
2. Go to the main page.
3. Check the graph of transactions per seconds.

Screenshots

An example of how many requests were made to get block data

Now the number will be lower

[xavier506]

LGTM