Add bridgetest and bridgetest.InitLogging

This allows modules outside of the bridge to test code that uses
`tfbridge.GetLogger`. This will be used by `dynamic`. It may also be used by AWS, which
currently has test code which uses the now moved-to-internal logging.InitContext.

pkg/bridgetest/README.md

@@ -0,0 +1,4 @@
+# bridgetest
+
+The `bridgetest` module adds facilities for providers to use when testing bridge
+integrations. Nothing in this module should be depended on for runtime functionality.

pkg/bridgetest/logging.go

@@ -0,0 +1,39 @@
+package bridgetest
+
+import (
+	"context"
+	"testing"
+
+	"github.com/pulumi/pulumi/sdk/v3/go/common/diag"
+	"github.com/pulumi/pulumi/sdk/v3/go/common/resource"
+	"github.com/pulumi/pulumi/sdk/v3/go/common/util/contract"
+
+	"github.com/pulumi/pulumi-terraform-bridge/v3/internal/logging"
+)
+
+// A sink that [tfbridge.GetLogger] can write to.
+type LoggingSink interface {
+	Log(context context.Context, sev diag.Severity, urn resource.URN, msg string) error
+	LogStatus(context context.Context, sev diag.Severity, urn resource.URN, msg string) error
+}
+
+type discardSink struct{}
+
+func (*discardSink) Log(context.Context, diag.Severity, resource.URN, string) error {
+	return nil
+}
+
+func (*discardSink) LogStatus(context.Context, diag.Severity, resource.URN, string) error {
+	return nil
+}
+
+// InitLogging equips ctx with a logger usable by [tfbridge.GetLogger].
+//
+//nolint:revive // Let t come before ctx.
+func InitLogging(t *testing.T, ctx context.Context, sink LoggingSink) context.Context {
+	contract.Assertf(t != nil, "t cannot be nil")
+	if sink == nil {
+		sink = &discardSink{}
+	}
+	return logging.InitLogging(ctx, logging.LogOptions{LogSink: sink})
+}