Add FromAttributeIndices helper to pprofile (#12176)

<!--Ex. Fixing a bug - Describe the bug and how this fixes the issue.
Ex. Adding a feature - Explain what this achieves.-->
#### Description

Profiles attributes are stored in a single `AttributeTable` attribute,
and then referenced in each substruct as `AttributeIndices`.

This means to read them as a `pcommon.Map`, a bit of pre-processing is
required.
This adds an helper method so each component manipulating profiles
doesn't have to reimplement it.

Benchmark:

```
go test -bench=BenchmarkFromAttributeIndices ./...
goos: darwin
goarch: arm64
pkg: go.opentelemetry.io/collector/pdata/pprofile
cpu: Apple M1 Max
BenchmarkFromAttributeIndices-10         9789714               123.2 ns/op           140 B/op          4 allocs/op
PASS
ok      go.opentelemetry.io/collector/pdata/pprofile    1.952s
PASS
ok      go.opentelemetry.io/collector/pdata/pprofile/pprofileotlp       0.407s
```

Author: dmathieu

.chloggen/pprofile-build-attributes.yaml

@@ -0,0 +1,25 @@
+# Use this changelog template to create an entry for release notes.
+
+# One of 'breaking', 'deprecation', 'new_component', 'enhancement', 'bug_fix'
+change_type: enhancement
+
+# The name of the component, or a single word describing the area of concern, (e.g. otlpreceiver)
+component: pdata/pprofile
+
+# A brief description of the change.  Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: Add new helper method `FromAttributeIndices` to build a `pcommon.Map` out of `AttributeIndices`.
+
+# One or more tracking issues or pull requests related to the change
+issues: [12176]
+
+# (Optional) One or more lines of additional information to render under the primary note.
+# These lines will be padded with 2 spaces and then inserted directly into the document.
+# Use pipe (|) for multiline entries.
+subtext:
+
+# Optional: The change log or logs in which this entry should be included.
+# e.g. '[user]' or '[user, api]'
+# Include 'user' if the change is relevant to end users.
+# Include 'api' if there is a change to a library API.
+# Default: '[user]'
+change_logs: [api]

pdata/pprofile/attributes.go

@@ -0,0 +1,28 @@
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+package pprofile // import "go.opentelemetry.io/collector/pdata/pprofile"
+
+import (
+	"go.opentelemetry.io/collector/pdata/pcommon"
+)
+
+type attributable interface {
+	AttributeIndices() pcommon.Int32Slice
+}
+
+// FromAttributeIndices builds a [pcommon.Map] containing the attributes of a
+// record.
+// The record can by any struct that implements an `AttributeIndices` method.
+// Updates made to the return map will not be applied back to the record.
+func FromAttributeIndices(table AttributeTableSlice, record attributable) pcommon.Map {
+	m := pcommon.NewMap()
+	m.EnsureCapacity(record.AttributeIndices().Len())
+
+	for i := 0; i < record.AttributeIndices().Len(); i++ {
+		kv := table.At(int(record.AttributeIndices().At(i)))
+		kv.Value().CopyTo(m.PutEmpty(kv.Key()))
+	}
+
+	return m
+}

pdata/pprofile/attributes_test.go

@@ -0,0 +1,64 @@
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+package pprofile
+
+import (
+	"fmt"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+
+	"go.opentelemetry.io/collector/pdata/pcommon"
+)
+
+func TestFromAttributeIndices(t *testing.T) {
+	table := NewAttributeTableSlice()
+	att := table.AppendEmpty()
+	att.SetKey("hello")
+	att.Value().SetStr("world")
+	att2 := table.AppendEmpty()
+	att2.SetKey("bonjour")
+	att2.Value().SetStr("monde")
+
+	attrs := FromAttributeIndices(table, NewProfile())
+	assert.Equal(t, attrs, pcommon.NewMap())
+
+	// A Location with a single attribute
+	loc := NewLocation()
+	loc.AttributeIndices().Append(0)
+
+	attrs = FromAttributeIndices(table, loc)
+
+	m := map[string]any{"hello": "world"}
+	assert.Equal(t, attrs.AsRaw(), m)
+
+	// A Mapping with two attributes
+	mapp := NewLocation()
+	mapp.AttributeIndices().Append(0, 1)
+
+	attrs = FromAttributeIndices(table, mapp)
+
+	m = map[string]any{"hello": "world", "bonjour": "monde"}
+	assert.Equal(t, attrs.AsRaw(), m)
+}
+
+func BenchmarkFromAttributeIndices(b *testing.B) {
+	table := NewAttributeTableSlice()
+
+	for i := range 10 {
+		att := table.AppendEmpty()
+		att.SetKey(fmt.Sprintf("key_%d", i))
+		att.Value().SetStr(fmt.Sprintf("value_%d", i))
+	}
+
+	obj := NewLocation()
+	obj.AttributeIndices().Append(1, 3, 7)
+
+	b.ResetTimer()
+	b.ReportAllocs()
+
+	for n := 0; n < b.N; n++ {
+		_ = FromAttributeIndices(table, obj)
+	}
+}