Fix the tests added by the merged PRs for all CI configurations

- discard the results of dump() and from_*() in CHECK_THROWS with
  utils::ignore_return_value (GCC -Werror=unused-result)
- give unit-bson's huge_string_t a default constructor (MSVC C2512,
  GCC 5, clang 3.5)
- unit-disabled_exceptions: use the literals namespace when the global
  UDLs are off (ci_test_noglobaludls; #5700)
- unit-binary_utf8_strict: expect the JSON pointer prefix with
  JSON_DIAGNOSTICS (#5741)
- skip the tests that rely on exceptions under JSON_NOEXCEPTION
  (#5678, #5732)
- clang-tidy and clang -Werror: static test data, CAPTURE(...);,
  const-correctness, use-after-move alias, unused conversion operator,
  a missing <iterator> include

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

tests/src/unit-comparison.cpp

@@ -969,7 +969,7 @@ TEST_CASE("copying an object preserves its comparator's state")
 
     for (const std::size_t depth : std::vector<std::size_t> {0, 127, 128, 200})
     {
-        CAPTURE(depth);
+        CAPTURE(depth)
 
         key_case_json original = object;
         for (std::size_t i = 0; i < depth; ++i)
@@ -1138,7 +1138,7 @@ TEST_CASE("operator<=> of binary values with a different subtype does not depend
     // and must still agree with the levels that do
     for (const std::size_t depth : std::vector<std::size_t> {0, 127, 128, 200})
     {
-        CAPTURE(depth);
+        CAPTURE(depth)
         const json x = deep(a, depth);
         const json y = deep(b, depth);
         CHECK((x <=> y) == std::partial_ordering::less); // *NOPAD*