Export of internal Abseil changes

--
d857e6e1f9b09a3eb5abd890677a98b23346f07a by Abseil Team <absl-team@google.com>:

Simplify internal TryAcquireWithSpinning.

No point declaring the `result` variable: we can just return the results
directly.

PiperOrigin-RevId: 307045800

--
421952252bc23be51f47f7d23f3422bad1ed382c by Derek Mauro <dmauro@google.com>:

Add custom sink support for `absl::Format()` through an ADL extension mechanism.

Users can now define
`void AbslFormatFlush(MySink* dest, absl::string_view part)`
to allow `absl::Format()` to append to a custom sink.

PiperOrigin-RevId: 306929052

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c73d5cdb62cd58ea421ed1aeeab78a0ffcfeeefb by Matt Calabrese <calabrese@google.com>:

Internal-only conformance-testing macro ABSL_INTERNAL_ASSERT_CONFORMANCE_OF for compile-time and runtime checks of a specified type, expected properties of that type, and a logically-ordered series of equivalence classes of that type.

PiperOrigin-RevId: 306885512

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a8c2495a07f37d68907855e3f0535bd5c27a3b52 by Abseil Team <absl-team@google.com>:

Internal change

PiperOrigin-RevId: 306766753
GitOrigin-RevId: d857e6e1f9b09a3eb5abd890677a98b23346f07a
Change-Id: Ic23c92ac74f9ffcbb2471ff8c6691f4b7b20354b

absl/strings/BUILD.bazel

@@ -651,6 +651,7 @@ cc_test(
     copts = ABSL_TEST_COPTS,
     visibility = ["//visibility:private"],
     deps = [
+        ":cord",
         ":str_format",
         ":strings",
         "//absl/base:core_headers",
@@ -666,8 +667,10 @@ cc_test(
     copts = ABSL_TEST_COPTS,
     visibility = ["//visibility:private"],
     deps = [
+        ":cord",
         ":str_format",
         ":str_format_internal",
+        ":strings",
         "@com_google_googletest//:gtest_main",
     ],
 )
@@ -726,6 +729,7 @@ cc_test(
     copts = ABSL_TEST_COPTS,
     visibility = ["//visibility:private"],
     deps = [
+        ":cord",
         ":str_format_internal",
         "@com_google_googletest//:gtest_main",
     ],