fix Boost::unit_test_framework linkage -- don't mix header & static library usage variants

[spoonincode]

Boost unit test framework can be used via header-only or by linking to a static library (or dynamic library). See https://www.boost.org/doc/libs/1_85_0/libs/test/doc/html/boost_test/usage_variants.html. Mixing these up can cause linker failures and/or ODR violations. If this sounds familiar, we previously had a mix ups fixed in AntelopeIO/leap#807. It appears we've mixed these up again in leap5 with the boost submodularization.

For example, in fc,

spring/libraries/libfc/CMakeLists.txt

Lines 105 to 106 in 09d979b

	target_link_libraries( fc PUBLIC Boost::date_time Boost::chrono Boost::iostreams Boost::interprocess Boost::multi_index Boost::dll
	Boost::multiprecision Boost::beast Boost::asio Boost::thread Boost::unit_test_framework Threads::Threads

The Boost::unit_test_framework target will link the Boost unit test static library. But then in test_fc the header-only usage variant is used,

spring/libraries/libfc/test/main.cpp

Lines 1 to 2 in 09d979b

	#define BOOST_TEST_MODULE libfc
	#include <boost/test/included/unit_test.hpp>

(of course, libfc linking to Boost::unit_test_framework is also undesirable on its own -- there is no reason nodeos should be linking to boost unit test framework)

This PR removes the Boost::unit_test_framework linkage from a number of base libraries -- appbase, fc, and chainbase -- and then adds the appropriate header-only Boost::included_unit_test_framework target where it is used. (curiously, chainbase_test appears to be the only remaining test leveraging the static library approach. I've left it as is, there is nothing wrong with that.)

Requires,

• when included in leap/spring, don't link Boost::unit_test_framework's static library as part of appbase library appbase#33
• when included in leap/spring, don't link Boost::unit_test_framework's static library as part of chainbase library chainbase#49

[spoonincode]

This is ugly but with the way libtester is currently written, anything it is linked to needs to have various boost unit test symbols defined.. and this is the best way without further refactor afaict

[ericpassmore]

Note:start
group: CLEANCODE
category: INTERNALS
summary: Consistently include Boost Test Framework, linking to library.
Note: end