Fix db error

[Neylix]

Description

Sometimes, we receveive message from different node asking to write a transaction in the DB. There is some case where the transaction is written 2 times in the DB and sometimes corrupt the file and so DB could not anymore read it.

So the idea is to create a queue that block the writing of a transaction if a writing is already happening on the same file.

Fixes #434

Type of change

• Bug fix (non-breaking change which fixes an issue)

How Has This Been Tested?

I added some log in the DB and we could see that their were mutiple transaction writing on the same file at the same time.
After update, mutuple writing on the same file are blocked and processed consecutively. So the error do not happen anymore.

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

[apoorv-2204]

Does it really worked?

[apoorv-2204]

yay!!

[apoorv-2204]

What about this? May be this, what do you think?

• Addition of check ChainIndex.transaction_exists, in write_transaction, to avoid multiple times writing of same transaction due to beacon transaction notification from other nodes. Under Subset code , write_transaction was being deployed with out any checks of transaction already exists, causing nb of nodes = nb of times same transactions written.
• 🗄️ , In file writer appending transaction, was not sequential resulting in corrupt chain file. If multiple transactions were deployed for same genesis address, then chain writer was deployed without any synchronous behaviour resulting in writing the same file which is being written by other process to same transaction file