Moved StorageTransaction to the fuel-core-storage crate

[xgreenx]

Closes #1589

Overview

The change moves the database transaction logic from the fuel-core to the fuel-core-storage level. The corresponding issue described the reason behind it.

Technical details of implementation

The change splits the KeyValueStore into KeyValueInspect and KeyValueMutate, as well the Blueprint into BlueprintInspect and BlueprintMutate. It allows requiring less restricted constraints for any read-related operations.

One of the main ideas of the change is to allow for the actual storage only to implement KeyValueInspect and Modifiable without the KeyValueMutate. It simplifies work with the databases and provides a safe way of interacting with them (Modification into the database can only go through the Modifiable::commit_changes). This feature is used to track the height of each database during commits and even limit how commits are done, providing additional safety. This part of the change was done as a separate commit.

The StorageTransaction is a StructuredStorage that uses StorageTransactionInner inside to accumulate modifications. Only StorageStorageInner has a real implementation of the KeyValueMutate(Other types only implement it in tests).

The implementation of the Modifiable for the Database contains a business logic that provides additional safety but limits the usage of the database. The Database now tracks its height and is responsible for its updates. In the commit_changes function, it analyzes the changes that were done and tries to find a new height(For example, in the case of the OnChain database, we are looking for a new Block in the FuelBlocks table).

As was planned in the issue, now the executor has full control over how commits to the storage are done.

All mutation methods now require &mut self - exclusive ownership over the object to be able to write into it. It almost negates the chance of concurrent modification of the storage, but it is still possible since the Database implements the Clone trait. To be sure that we don't corrupt the state of the database, the commit_changes function implements additional safety checks to be sure that we commit updates per each height only once time.

Side changes:

• The drop function was moved from Database to RocksDB as a preparation for the state rewind since the read view should also keep the drop function until it is destroyed.
• The StatisticTable table lives in the off-chain worker.
• Removed duplication of the Database from the dapp::ConcreteStorage since it is already available from the VM.
• The executor return only produced Changes instead of the storage transaction, which simplifies the interaction between modules and port definition.
• The logic related to the iteration over the storage is moved to the fuel-core-storage crate and is now reusable. It provides an interator method that duplicates the logic from MemoryStore on iterating over the BTreeMap and methods like iter_all, iter_all_by_prefix, etc. It was done in a separate revivable commit.
• The MemoryTransactionView is fully replaced by the StorageTransactionInner.
• Removed flush method from the Database since it is not needed after Fix for the long database initialization after restart #1664 .

[xgreenx]

Moved default implementation from the Database here

[bvrooman]

47 / 86 files reviewed so far, will continue tomorrow

[bvrooman]

Reviewed all 86 files at the time of this comment. A couple of small nits and questions. If you are still interested in doing a group review, that may be helpful for a better understanding of the PR from a high level.

[Dentosal]

Ok I think this is finally good to go. Phew.