Switch away from doctest, and drop it

[pinotree]

There is only one test using doctest instead of catch2; hence, switch it to catch2, so doctest can be dropped.

This is also prompted by the fact that the old doctest copy does not build with glibc 2.34 (released 2 years ago [1]), because SIGSTKSZ is no more a constant; this was fixed long ago in doctest upstream [2][3]. Since we can get away from doctest, let's get rid of it rather than patching/updating an old copy.

[1] https://sourceware.org/pipermail/libc-alpha/2021-August/129718.html [2] https://github.com/doctest/doctest/issues/473 [3] https://github.com/doctest/doctest/commit/099d5414e97244ec44cf46b14cd176b3a3dc52e3

[codecov-commenter]

Codecov Report

Merging #266 (b133b77) into master (8872e23) will not change coverage. The diff coverage is 100.00%.

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@@           Coverage Diff           @@
##           master     #266   +/-   ##
=======================================
  Coverage   90.53%   90.53%           
=======================================
  Files         119      119           
  Lines       12144    12144           
=======================================
  Hits        10994    10994           
  Misses       1150     1150           

Files Changed	Coverage Δ
test/experimental/dvektor.cpp	100.00% <100.00%> (ø)

[arximboldi]

Thank you very much!