core: introduce new tracing hooks prior to transaction execution and after block reward application

[jwasinger]

Add two new tracing hooks which are called:

• immediately before the first transaction in a block would be executed (even if the block is empty).
• after applying block rewards as the final step in block execution.

These are required for BALs:

1. if the block is empty, there is no way to differentiate between the execution of pre/post transaction block state changes. In the access list, these are distinct.
2. Even though 1 only necessitates the addition of a single hook which is called immediately before execution of the first transaction in the block, having a dedicated hook which is called post-block-reward-application makes the implementation of the access list cleaner.

[s1na]

if the block is empty, there is no way to differentiate between the execution of pre/post transaction block state changes. In the access list, these are distinct.

Which state changes are those?

[jwasinger]

The beacon root and parent root accumulator contracts mutate their storage. Post-block, contract-based withdrawals and EIP-4895 withdrawals can mutate account balances.

[s1na]

It should be possible to use the OnSystemCallStart, OnSystemCallEnd to detect changes that happen during any of that.

[jwasinger]

It should be possible to use the OnSystemCallStart, OnSystemCallEnd to detect changes that happen during any of that.

There's no way to determine when the system calls are pre/post-transactions if the block does not contain any transactions.

[jwasinger]

Closing this. I am able to use the system-contract start/end hooks as-is without introducing new ones. It's not super elegant but I think it will work.