This fixes a compilation error in chronik_bridge
```
/home/pierre/dev/bitcoin-abc/chronik/chronik-cpp/chronik_bridge.cpp:240:45: required from here
/usr/include/c++/11/bits/stl_algobase.h:385:25: error: no match for ‘operator=’ (operand types are ‘std::back_insert_iterator<rust::cxxbridge1::Vec<unsigned char> >’ and ‘const std::byte’)
```
I broke these functions in D15935. The underlying data type for CDataStream is now std::byte instead of `uint8_t`, so we need to cast the streams before passing them to `chronik::util::ToRustVec<uint8_t>`