Fix test lints that are red on develop (effc++, clang-tidy) (#5946)

- unit-bson: initialize the SAX recorder's member (-Weffc++)
- unit-json_patch: build the reference document independently instead of
  copying it (performance-unnecessary-copy-initialization)
- unit-json_view_builder: use node_kind::link instead of an out-of-range
  enum cast (clang-analyzer-optin.core.EnumCastOutOfRange)

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

tests/src/unit-json_view_builder.cpp

@@ -592,7 +592,7 @@ TEST_CASE("json_view node integer bits")
                 })
         {
             CAPTURE(v)
-            n.kind = static_cast<nlohmann::detail::view::node_kind>(0x5A);
+            n.kind = nlohmann::detail::view::node_kind::link;
             n.flags = 0xA5;
             n.extra = 0x1234;
             n.off = 0x89ABCDEFu;
@@ -601,7 +601,7 @@ TEST_CASE("json_view node integer bits")
             CHECK(n.len == static_cast<std::uint32_t>(v));
             CHECK(n.next == static_cast<std::uint32_t>(v >> 32));
             // the other fields are untouched
-            CHECK(static_cast<std::uint8_t>(n.kind) == 0x5A);
+            CHECK(n.kind == nlohmann::detail::view::node_kind::link);
             CHECK(n.flags == 0xA5);
             CHECK(n.extra == 0x1234);
             CHECK(n.off == 0x89ABCDEFu);