Fix catch_discover_tests() from breaking on long test names

[Quincunx271]

Fixes #1645 by rolling back d4eec01 ; reopens #1590 .

Parsing --list-tests is broken, as Catch automatically line wraps the line when it gets too long, stripping any whitespace in the process. This means that it's impossible to reproduce the exact name of the
test if the test's name is long enough to line-wrap.

Furthermore, overwriting the LABELS property with the discovered labels breaks users who manually added custom ctest labels. However, this seems to not actually overwrite the labels due to buggy handling of our strange test names by CMake.

Rolling back to using --list-test-names-only for now, as it does not wrap lines even on very long test names.

We may be able parse the output of --list-tags to produce the ctest labels. However, the straightforward way of doing this is to use CMake's get_property(TEST ...) and set_property(TEST ... APPEND ...), which don't work if the test name has spaces or other special characters. Such test names may be illegal test names anyway—the documentation doesn't state whether it's allowed or disallowed for the variant of add_test(...) we are using—although they appear to work.

Upstream CMake issue on allowing custom strings as test names, or at least custom test descriptions: https://gitlab.kitware.com/cmake/cmake/issues/19391

[Quincunx271]

I have a partial implementation of making Catch labels work as CTest labels: https://github.com/Quincunx271/Catch2/blob/3047ee81052b35f9867b61c15a81c9df2b539621/contrib/CatchAddTests.cmake . But this is broken due to the handling of get_property(TEST ...) and set_property(TEST ... APPEND ...) as mentioned above.

[codecov]

Codecov Report

Merging #1658 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #1658   +/-   ##
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  Coverage   83.66%   83.66%           
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  Files         123      123           
  Lines        3403     3403           
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  Hits         2847     2847           
  Misses        556      556

[codecov]

Codecov Report

Merging #1658 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #1658   +/-   ##
=======================================
  Coverage   83.66%   83.66%           
=======================================
  Files         123      123           
  Lines        3403     3403           
=======================================
  Hits         2847     2847           
  Misses        556      556

[horenmar]

Looks good and it is good to hear that the test name restriction is likely to be lifted.