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/raw_hash_map.h

@@ -109,6 +109,9 @@ class raw_hash_map : public raw_hash_set<Policy, Hash, Eq, Alloc> {
     return insert_or_assign(k, v).first;
   }
 
+  // All `try_emplace()` overloads make the same guarantees regarding rvalue
+  // arguments as `std::unordered_map::try_emplace()`, namely that these
+  // functions will not move from rvalue arguments if insertions do not happen.
   template <class K = key_type, class... Args,
             typename std::enable_if<
                 !std::is_convertible<K, const_iterator>::value, int>::type = 0,