vendor: update buildkit to v0.18.0-rc1

Signed-off-by: Tonis Tiigi <tonistiigi@gmail.com>

vendor/go.opentelemetry.io/otel/sdk/metric/internal/exemplar/reservoir.go

@@ -0,0 +1,32 @@
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+package exemplar // import "go.opentelemetry.io/otel/sdk/metric/internal/exemplar"
+
+import (
+	"context"
+	"time"
+
+	"go.opentelemetry.io/otel/attribute"
+)
+
+// Reservoir holds the sampled exemplar of measurements made.
+type Reservoir interface {
+	// Offer accepts the parameters associated with a measurement. The
+	// parameters will be stored as an exemplar if the Reservoir decides to
+	// sample the measurement.
+	//
+	// The passed ctx needs to contain any baggage or span that were active
+	// when the measurement was made. This information may be used by the
+	// Reservoir in making a sampling decision.
+	//
+	// The time t is the time when the measurement was made. The val and attr
+	// parameters are the value and dropped (filtered) attributes of the
+	// measurement respectively.
+	Offer(ctx context.Context, t time.Time, val Value, attr []attribute.KeyValue)
+
+	// Collect returns all the held exemplars.
+	//
+	// The Reservoir state is preserved after this call.
+	Collect(dest *[]Exemplar)
+}