apmotel: native transaction are always considered non-recording when retrieved from Otel's trace.SpanFromContext

[wzy9607]

Describe the bug

After started a apm transaction, apm.TransactionFromContext(ctx).Sampled() and Otel's trace.SpanFromContext(ctx).IsRecording() returns different result.
the later is always false.

To Reproduce

package main

import (
	"context"
	"fmt"
	"testing"

	"github.com/stretchr/testify/assert"
	"go.elastic.co/apm/module/apmotel/v2"
	"go.elastic.co/apm/v2"
	"go.elastic.co/apm/v2/apmtest"
	"go.opentelemetry.io/otel"
	"go.opentelemetry.io/otel/trace"
)

func Test_a(t *testing.T) {
	t.Parallel()
	tracer := apmtest.NewRecordingTracer()
	provider, err := apmotel.NewTracerProvider(apmotel.WithAPMTracer(tracer.Tracer))
	if err != nil {
		panic(err)
	}
	otel.SetTracerProvider(provider)

	ctx := context.Background()
	tx := tracer.StartTransaction("test1", "test")
	ctx = apm.ContextWithTransaction(ctx, tx)

	tx = apm.TransactionFromContext(ctx)
	sp := trace.SpanFromContext(ctx)
	fmt.Printf("apm transaction: %#v\n", tx)
	fmt.Printf("OTel span: %#v\n", sp)
	assert.Equal(t, tx.Sampled(), sp.IsRecording())
}

Expected behavior

Expect the assert to not fail.