Cmake labels (take-over #2832)

[Bidski]

Continuing where @uyha (#2690) and @LecrisUT (#2832) left off

Adds a CMake reporter to list test cases.

Test cases are reported as a CMake list of lists with list elements wrapped in long form arguments.

Here is example output from ./debug-build/tests/ctest-registration-test/tests --reporter cmake --list-tests

[[[=[@Script[C:\EPM1A]=x;"SCALA_ZERO:"]=];[=[]=];[=[/home/abiddulph/Projects/Catch2/tests/TestScripts/DiscoverTests/register-tests.cpp]=];[=[11]=];[=[[==[script regressions]==]]=]]];[[[=[Some test]=];[=[]=];[=[/home/abiddulph/Projects/Catch2/tests/TestScripts/DiscoverTests/register-tests.cpp]=];[=[12]=];]];[[[=[Let's have a test case with a long name. Longer. No, even longer. Really looooooooooooong. Even longer than that. Multiple lines worth of test name. Yep, like this.]=];[=[]=];[=[/home/abiddulph/Projects/Catch2/tests/TestScripts/DiscoverTests/register-tests.cpp]=];[=[13]=];]];[[[=[And now a test case with weird tags.]=];[=[]=];[=[/home/abiddulph/Projects/Catch2/tests/TestScripts/DiscoverTests/register-tests.cpp]=];[=[16]=];[=[[==[foo,bar]==];[==[tl;dr]==];[==[tl;dw]==]]=]]]

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 76.82927% with 19 lines in your changes missing coverage. Please review.

Project coverage is 90.97%. Comparing base (4e8d92b) to head (c69ca3d). Report is 22 commits behind head on devel.

Additional details and impacted files

@@            Coverage Diff             @@
##            devel    #2871      +/-   ##
==========================================
- Coverage   91.10%   90.97%   -0.12%     
==========================================
  Files         198      199       +1     
  Lines        8493     8575      +82     
==========================================
+ Hits         7737     7801      +64     
- Misses        756      774      +18     

[horenmar]

I just noticed that this PR was supposed to supersede the previous work using the JSON reporter.

Sorry for keeping it open this long, but this is a hard no. I am not interested in adding a CMake-specific test lister to the default build.