Fix the CI failures that the first failing TU of each job hid

- unit-stream-bulk-scan: compute the claimed size without a condition;
  the tag-dispatched template was unused with a 64-bit std::size_t
  (-Wunused-template)
- unit-json_view: give failing_allocator the typedefs, rebind and
  members that GCC 4.8's std::map takes from the allocator directly
- clang-tidy hits in the tests from #5997: raw string literals
  (unit-json_view), redundant c_str() and a NOLINT for &text[0]
  (unit-locale-cpp), reserve() before a loop (unit-ordered_json), and a
  NOLINT for a return that a braced list would turn into an array
  (unit-regression1)

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

tests/src/unit-ordered_json.cpp

@@ -541,6 +541,7 @@ TEST_CASE("object_key_index")
         };
 
         std::vector<std::size_t> hashes;
+        hashes.reserve(initial);
         for (std::size_t i = 0; i < initial; ++i)
         {
             hashes.push_back(hash_of(i));