Fix last oracle chain loaded in mem table loader init

[Neylix]

Description

When a node restart, it loads the past oracle summary in memory, but it do not load the last oracle transaction.
In some case the next self repair after the bootstrap may failed caused by an invalid_transaction_fee error.
So, during init Oracle Mem Table Loader also load the last oracle chain transactions

Type of change

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

How Has This Been Tested?

To reproduce the error:

• start 3 node and wait them to be authorized
• after an oracle summary, wait for the next oracle transaction (normally coming just after summary)
• stop a node
• send a transfer transaction
• restart the node after other set it as unavailable

On the next self repair, the restarted node should have a invalid transaction fee error.

With the fix 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