test: split and improve ObjectFieldMapTypeHandlerFactoryTests

[jdrueckert]

• split into multiple tests to avoid testing different aspects in single test
• remove usage of implicit member type knowledge in assertion phase
• add negative assertions to ensure only expected calls are made
• improve test case documentation

Once #5154 is merged, we'll need to update the suppression of UUF_UNUSED_FIELD spotbugs findings for SingleTypeClass and MultiTypeClass.

[skaldarnar]

I'd like to explain what we are doing here at least once.

Also, I'd move the specific test up (test happy path) and then make the "negative tests" afterwards.

Suggested change

	verify(typeHandlerLibrary, times(1)).getTypeHandler((Type) any());
	verify(typeHandlerLibrary, times(1)).getTypeHandler(eq(TypeInfo.of(Integer.class).getType()));
	verify(typeHandlerLibrary, never()).getTypeHandler((Class<Object>) any());
	verify(typeHandlerLibrary, never()).getTypeHandler((TypeInfo<Object>) any());
	// verify that the expected typehandler was created
	verify(typeHandlerLibrary, times(1)).getTypeHandler(eq(TypeInfo.of(Integer.class).getType()));
	// verify that creation was triggered only for the expected typehandler, but not for others
	// 'getTypeHandler' can be called with either Type, Class, or TypeInfo, and we only expect one call with Type
	verify(typeHandlerLibrary, times(1)).getTypeHandler((Type) any());
	verify(typeHandlerLibrary, never()).getTypeHandler((Class<Object>) any());
	verify(typeHandlerLibrary, never()).getTypeHandler((TypeInfo<Object>) any());

[jdrueckert]

Failing test ExampleTest.testClientConnection is a known sporadic and unrelated to code changes in this PR.
Merging despite the failing test.