add new Api to get beacon chain aggregate

[tenmoves]

Description

Since the PR #559 beacon and beacon summaries are not anymore transactions. Before we could get these transaction using graphql API networkTransaction, but now we don't have any way to get the summary data.

We create a new schema in graphql like beaconSummary with a timestamp in parameter which returns the beacon aggregate for this date.
If the date is the last summary date, API should use beacon summary and not beacon aggregate as it is done in explorer.

example graphql query

{
  beaconChainSummary(timestamp: 1670369760) {
    version
    p2pAvailabilities
    summaryTime
    availabilityAddingTime
    transactionSummaries(limit: 1, pagingOffset: 2) {
      fee
      type
      timestamp
      address
      movementsAddresses
    }
  }
}

Fixes #639

Type of change

Please delete options that are not relevant.

• New feature (non-breaking change which adds functionality)

How Has This Been Tested?

Please describe the tests that you ran to verify your changes. Provide instructions so we can reproduce. Please also list any relevant details for your test configuration

• Tested locally in graphiQl
• Unit tests

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in downstream modules

[samuelmanzanera]

I think there is a problem with the summary time

The summary should not be DateTime.utc_now but the next summary time.
This is causing the no display of the last transactions recorded.

[bchamagne]

I think there's something wrong with the dates (I might be wrong)

No timestamp given: I can see my transfer

I added the timestamp that is the date of the transfer: there is nothing

Same timestamp as above but a minute later (1 slot later): the date changed to slot - 1

[tenmoves]

@bchamagne the behaviour you have detected is because you only have a single node running.
I tested with multiple nodes and it seem to work (after I fixed other unrelated issues).