Cherry-picked from develop branch commit 4dc3836449
ignoring changes in all `CMakeLists.txt` files but this one
`test/extension/toolbox/CMakeLists.txt` which somehow missed the changes.
Possibly due to my mistake during previous cherry-picks to compose
the emergency fix#394 for docs in `master` branch, that also
brought the restructuring of the tests directories.
Missing changes in `test/extension/toolbox/CMakeLists.txt` file
are currently causing failures of AzP builds using CMake
for `master` Boost 1.72 merge e8a04f403e
This is attempt to fix it in the `master`.
Split header tests accordingly i.e. test core headers as part of
core tests, numeric extension headers as part of numeric tests, etc.
It extends the convention of sub-directories already established in
`include/boost/gil` directory. It is sensible to follow it in other
areas of the source tree (i.e. `test/`, `doc/` and `benchmark/`).
Another important reason to move the tests is to enable removal of
the top-level `Jamfile` with all its definitions of test-specific
requirements.
The top-level `Jamfile` is not advised, especially if it specifies
build requirements like C++ language version.
Those affect non-tests builds e.g. documentation, causing failures
during generation of HTML documentation (leads to missing docs).
(cherry picked from develop branch commit 4ed7701b47)
