Rename hashtablez `Sample()` to `SampleForTesting()`.

`Sample()` in `hashtablez_sampler.h` is only used by hashtablez tests; `raw_hash_set` calls `ShouldSampleNextTable()` and `ForcedTrySample()` directly. Rename it to make the intent explicit.

PiperOrigin-RevId: 1009579332

absl/container/internal/hashtablez_sampler.h

diff --git a/absl/container/internal/hashtablez_sampler.h b/absl/container/internal/hashtablez_sampler.h
index 9e9a47c..628acf6 100644
--- a/absl/container/internal/hashtablez_sampler.h
+++ b/absl/container/internal/hashtablez_sampler.h
@@ -247,9 +247,11 @@
 // It is useful to avoid sampling attempts and sampling delays in tests.
 void TestOnlyRefreshSamplingStateForCurrentThread();
 
-// Returns a sampling handle.
-inline HashtablezInfoHandle Sample(size_t inline_element_size, size_t key_size,
-                                   size_t value_size, uint16_t soo_capacity) {
+// Returns a sampling handle. For use in tests only: `raw_hash_set` calls
+// `ShouldSampleNextTable()` and `ForcedTrySample()` directly.
+inline HashtablezInfoHandle SampleForTesting(size_t inline_element_size,
+                                             size_t key_size, size_t value_size,
+                                             uint16_t soo_capacity) {
   if (ABSL_PREDICT_TRUE(!ShouldSampleNextTable())) {
     return HashtablezInfoHandle(nullptr);
   }

absl/container/internal/hashtablez_sampler_test.cc

diff --git a/absl/container/internal/hashtablez_sampler_test.cc b/absl/container/internal/hashtablez_sampler_test.cc
index 0d863a8..b61976d 100644
--- a/absl/container/internal/hashtablez_sampler_test.cc
+++ b/absl/container/internal/hashtablez_sampler_test.cc
@@ -332,10 +332,10 @@
   double sample_rate = 0.0;
   for (int i = 0; i < 1000000; ++i) {
     HashtablezInfoHandle h =
-        Sample(test_element_size,
-               /*key_size=*/test_key_size, /*value_size=*/test_value_size,
-
-               /*soo_capacity=*/0);
+        SampleForTesting(test_element_size,
+                         /*key_size=*/test_key_size,
+                         /*value_size=*/test_value_size,
+                         /*soo_capacity=*/0);
 
     ++total;
     if (h.IsSampled()) {