Improve test-naming abilities for parameterized tests

[tophyr]

Catch2 generates names for the TEMPLATE_* style test definition macros, and the naming can be improved somewhat. This PR adds the ability to control the separator - for situations where external forces might preclude things like spaces in a test name - and also the ability to specify a string associated with a type for a template-list test.

Addresses Issue https://github.com/catchorg/Catch2/issues/2542

[codecov[bot]]

Codecov Report

Merging #2771 (df90ea3) into devel (53d0d91) will increase coverage by 0.04%. The diff coverage is 100.00%.

Additional details and impacted files

@@            Coverage Diff             @@
##            devel    #2771      +/-   ##
==========================================
+ Coverage   91.51%   91.55%   +0.04%     
==========================================
  Files         198      199       +1     
  Lines        8243     8246       +3     
==========================================
+ Hits         7543     7549       +6     
+ Misses        700      697       -3     

[tophyr]

I've ended up eliminating the RTTI sections of this PR - users can look up RTTI in their IndexedTestTypeName<> implementations if they choose. The compiler differences around RTTI complicate testing to the point that I'll stick that stuff in a different PR.

[tophyr]

@horenmar when you get some time, would love eyes on this and any feedback or thoughts.

[tophyr]

Rebased to 3.5.0

[tophyr]

pingping @horenmar