Updates multiplexer to make requests complete with error_code() rather than error_code(0)
Integration tests now use io_context::run_for to run with a timeout and avoid deadlocks
Tests now use concrete lambdas where generic ones are not required
Tests now use BOOST_TEST with operator== to print values on error
Tests now use anonymous namespaces to detect dead code
Adds run_coroutine_test and removed start from common.hpp
Updates test_reconnect to perform relevant checks
Refactors how test_issue_50 launches its coroutines
Groups tests in CMake as unit or integration
Updates Jamfile tests to contain all unit tests and only unit tests
