CMake test integration

[ThomasAdam]

Hi,

This PR introduces the following commits:

• build: cmake: enable tests

This adds the ability to compile tests as part of using CMake.

Note that, I've had to unwrap some ucl_*() calls from assert() (see comment below on this PR.)

I've also explicitly disabled the tests from running on Windows, as they've not been written with that in mind. However, I have still changed some of the tests in terms of their headers, should we revisit this in the future.

• build: github: add flags to ctest

This adds a few flags to Github actions to make ctest easier to deal with.

• build: configure: remove duplicate test

I noticed a duplicate test; msgpack. I presume this is meant to be
test_streaming but this test is broken currently, and hasn't explicitly been running as a test (only compiled).

[ThomasAdam]

It looks as though this is failing due to -DCMAKE_BUILD_TYPE=Release -- will check later why this is causing the generate test to fail.

[ThomasAdam]

This PR is now ready for review.

The reason the generate test was failing is due to the fact that when you do a CMAKE_BUILD_TYPE=Release, this explicitly passes -DNDEBUG which will disable the use of assert().

There's definitely something possibly amiss here, as this is a bit of an odd situation.

For now, I've explicitly removed some url_*() calls which were being wrapped by assert().

I don't think it'll be a big issue overall.

But the tests could do with some love, I know...