Fix ClangTidy warnings in btree.h and btree_test.cc.

PiperOrigin-RevId: 471639724
Change-Id: Ie609f4d5b15c06fc286fae2944b550937da266d3

absl/container/BUILD.bazel

@@ -959,7 +959,6 @@ cc_test(
         "//absl/flags:flag",
         "//absl/hash:hash_testing",
         "//absl/memory",
-        "//absl/meta:type_traits",
         "//absl/strings",
         "//absl/types:compare",
         "@com_google_googletest//:gtest_main",

absl/container/CMakeLists.txt

@@ -81,7 +81,6 @@ absl_cc_test(
     absl::raw_logging_internal
     absl::strings
     absl::test_instance_tracker
-    absl::type_traits
     GTest::gmock_main
 )
 

absl/container/btree_test.cc

@@ -18,6 +18,7 @@
 #include <array>
 #include <cstdint>
 #include <functional>
+#include <iterator>
 #include <limits>
 #include <map>
 #include <memory>
@@ -26,6 +27,7 @@
 #include <string>
 #include <type_traits>
 #include <utility>
+#include <vector>
 
 #include "gmock/gmock.h"
 #include "gtest/gtest.h"
@@ -38,7 +40,6 @@
 #include "absl/flags/flag.h"
 #include "absl/hash/hash_testing.h"
 #include "absl/memory/memory.h"
-#include "absl/meta/type_traits.h"
 #include "absl/strings/str_cat.h"
 #include "absl/strings/str_split.h"
 #include "absl/strings/string_view.h"

absl/container/internal/btree.h

@@ -1242,7 +1242,7 @@ class btree {
     // MSVC has constexpr code generations bugs here.
     EmptyNodeType() : parent(this) {}
 #else
-    constexpr EmptyNodeType(node_type *p) : parent(p) {}
+    explicit constexpr EmptyNodeType(node_type *p) : parent(p) {}
 #endif
   };