Ever since we #5913 have been sending invalid reject messages
for transactions and blocks.
test: Add basic test for `reject` code
Extend P2P test framework to make it possible to expect reject
codes for transactions and blocks.
Github-Pull: #7179
Rebased-From: 9fc6ed6003da42f035309240c715ce0fd063ec03 20411903d7b356ebb174df2daad1dcd5d6117f79