Split TEMPLATE_TEST* macros into their own set of files

These files are not included by the default
`#include <catch2/catch_test_macros.hpp>` path, so that users do
not have to pay for them if they do not use them. Follow up is to
split out the small part of `catch_preprocessor.hpp` used by the
default test macros (AFAIK, it is just `INTERNAL_CATCH_REMOVE_PARENS`
macro), so that it is not included by the default path either.

Also fixes #1892 by providing the missing macros.

tests/SelfTest/UsageTests/Class.tests.cpp

@@ -4,6 +4,7 @@
  */
 
 #include <catch2/catch_test_macros.hpp>
+#include <catch2/catch_template_test_macros.hpp>
 #include <array>
 
 namespace{ namespace ClassTests {

tests/SelfTest/UsageTests/Misc.tests.cpp

@@ -4,6 +4,7 @@
  */
 
 #include <catch2/catch_test_macros.hpp>
+#include <catch2/catch_template_test_macros.hpp>
 
 #ifdef __clang__
 #   pragma clang diagnostic ignored "-Wc++98-compat"