The current Catch version (1.9.6) in the codebase is incompatible with CXX23

[pachadotdev]

CXX23 is strict about the lhs operand, which means the current Catch version (1.9.6) used with testthat will cause multiple compilation errors not because of the tested package but because of the vendored Catch header.

In #2278 I added the scripts I used to use Catch2 with testthat after noticing that cpp4r does not pass all tests when enforcing CXX23 with the GNU compiler.