refactor(indexer,graphql): optimize transaction execution flow

[kodemartin]

Description of change

This patch refactors the optimistic transaction execution flow in iota-indexer. The main motivation is to avoid the redundant database queries in the Mutation.executeTransactionBlock as identified in #8775.

The changes implemented have been dictated by the observation that GraphQL only requires the transaction ingested after execution, let it be either optimistic or checkpointed.

We therefore decouple execution and ingestion from constructing the JSON-RPC response in iota_indexer::optimistic_indexing. This leads to a series of simplifications both in iota-indexer and particularly in iota-graphql-rpc.

In summary:

• We introduce a new IngestionPath enum that represents the dual possibility of ingestion in this context: Optimistic or Checkpoint. This is the returned by OptimisticExecutor::execute_and_index_transaction.
• Building the JSON-RPC response is delegated directly in OptimisticWriteApi where it fits the scope more.
• GraphQL uses IngestionPath to construct the TransactionBlockEffects required for the associated response, and the errors are generated by the available methods of the latter.

Links to any relevant issues

Fixes #8775

How the change has been tested

• Basic tests (linting, compilation, formatting, unit/integration tests)
• Patch-specific tests (correctness, functionality coverage)

Release Notes

• GraphQL: Optimize Mutation.executeTransactionBlock.

[sergiupopescu199]

lgtm 🎸