This change improves reusability of the EVM struct. Two methods are added:

- SetBlockContext(...)
- SetTracer(...)

Other attributes like the TransactionContext and the StateDB can already be updated.
BlockContext and Tracer are partially not updateable right now. This change fixes it and
opens the potential to reuse an EVM struct in more ways.
Co-authored-by: Felix Lange <fjl@twurst.com>