Export of internal Abseil changes

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0f6565955231dc74ebad62ef32a18c457afa2dc7 by Abseil Team <absl-team@google.com>:

Document guarantee that we do not move from rvalue arguments if no insertion happens with absl::raw_hash_map::try_emplace, as done with std::unordered_map::try_emplace.

PiperOrigin-RevId: 264430409

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292e6b9e08fa689e8400d7f2db94cbcab29d5889 by CJ Johnson <johnsoncj@google.com>:

Removes use of aligned_storage in FixedArray and InlinedVector in favor of aligned char buffers.

PiperOrigin-RevId: 264385559

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aa0b19ad11ae5702022feee0e2e6434cfb28c9e9 by Derek Mauro <dmauro@google.com>:

Make the unit tests for absl::any, absl::optional, and absl::variant
no-ops when these types are just aliases for the corresponding std::
types. We have no way to fix standard library implementation bugs, so
don't bother working around them.

Also disable the corresponding exception-safety tests as well when
exceptions are not enabled.

Fixes https://github.com/abseil/abseil-cpp/pull/360

PiperOrigin-RevId: 264382050

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65896a911f36481b89b4712c83b91c90a76b64e8 by Abseil Team <absl-team@google.com>:

Improve documentation on erase

PiperOrigin-RevId: 264381266
GitOrigin-RevId: 0f6565955231dc74ebad62ef32a18c457afa2dc7
Change-Id: I74b9bd2ddf84526014104f17e87de70bd3fe65fa

absl/container/internal/hash_generator_testing.h

@@ -19,6 +19,7 @@
 #define ABSL_CONTAINER_INTERNAL_HASH_GENERATOR_TESTING_H_
 
 #include <stdint.h>
+
 #include <algorithm>
 #include <iosfwd>
 #include <random>
@@ -27,6 +28,7 @@
 #include <utility>
 
 #include "absl/container/internal/hash_policy_testing.h"
+#include "absl/memory/memory.h"
 #include "absl/meta/type_traits.h"
 #include "absl/strings/string_view.h"
 
@@ -129,6 +131,13 @@ struct Generator<std::tuple<Ts...>> {
   }
 };
 
+template <class T>
+struct Generator<std::unique_ptr<T>> {
+  std::unique_ptr<T> operator()() const {
+    return absl::make_unique<T>(Generator<T>()());
+  }
+};
+
 template <class U>
 struct Generator<U, absl::void_t<decltype(std::declval<U&>().key()),
                                 decltype(std::declval<U&>().value())>>