Add missing headers so that all headers compile independently

[vissarion]

Fixes #523

Also adds a github actions script to test that all headers compile independently.

[awulkiew]

Is this newly added test very heavy? All of the files in the library are compiled. AFAIR we decided not to run it automatically because it takes a lot of time. How long does it take vs minimal and documentation tests?

[vissarion]

Good point. I think it was not to run automatically because it was failing (see #525 (comment)). Also this PR does not change that, it still do not run automatically but only called by the new github action.

Regarding performance I got the following timings (on my laptop with clang-15)

test	time
b2 test/headers/ -j8	6m54.947s
b2 toolset=clang cxxstd=14,17,2a variant=debug,release address-model=32,64 test//minimal -j8	0m56.863s
b2 libs/geometry/doc/src/examples -j8	2m21.983s
cd boost/geometry/doc; b2 -j8	1m0.406s

Note that for the minimal test the timing refers to testing only 1 out of 14 compilers.

So roughly speaking the headers test is the 1/3 of the current tests run on actions (i.e. minimal & documentation). It is somehow heavy I agree.

Alternatively, we can enable it only for push and not for PRs or even add it to circleCI (where the percentage over the total test time would be much smaller).

[vissarion]

@awulkiew the new test has picked up by github actions so now you can also check the times in the server; i.e. 20m for headers vs. 4-11m for each minimal test.

[barendgehrels]

Thanks! I didn't review all changes in detail, but in general it looks good to me.

[awulkiew]

Right, so it doesn't take that long vs all of the tests, since it's done only once. Thanks!