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?