[exporter/awskinesis] use cached credentials provider (#32415)

**Description:** 

Wraps the `AssumeRoleProvider` in a `CachedCredentials` provider, in the
case the AWS role is explicitly specified in the configuration. This
prevents a role assumption from happening every API call.

This was causing us to get rate limited by AWS STS since it was not
caching credentials.

The previous configuration basically fulfills the scenario described in
the AWS [Go SDK V2
docs](https://aws.github.io/aws-sdk-go-v2/docs/configuring-sdk/#specify-credentials-programmatically):
> All credential providers passed to or returned by LoadDefaultConfig
are wrapped in a
[CredentialsCache](https://pkg.go.dev/github.com/aws/aws-sdk-go-v2/aws#CredentialsCache)
automatically. This enables caching and concurrency safe credential
access. If you explicitly configure a provider on aws.Config directly
you must explicitly wrap the provider with this type using
[NewCredentialsCache](https://pkg.go.dev/github.com/aws/aws-sdk-go-v2/aws#NewCredentialsCache).

**Link to tracking Issue:** N/A

**Testing:** N/A

.chloggen/awskinesis_cached-credentials.yaml

@@ -0,0 +1,6 @@
+change_type: bug_fix
+component: awskinesisexporter
+note: Wraps the `AssumeRoleProvider` in a `CachedCredentials` provider, in the case the AWS role is specified. This prevents a role assumption from happening every API call.
+issues: [32415]
+subtext:
+change_logs: [user]

exporter/awskinesisexporter/exporter.go

@@ -65,10 +65,11 @@ func createExporter(ctx context.Context, c component.Config, log *zap.Logger, op
 	var kinesisOpts []func(*kinesis.Options)
 	if conf.AWS.Role != "" {
 		kinesisOpts = append(kinesisOpts, func(o *kinesis.Options) {
-			o.Credentials = stscreds.NewAssumeRoleProvider(
+			roleProvider := stscreds.NewAssumeRoleProvider(
 				sts.NewFromConfig(awsconf),
 				conf.AWS.Role,
 			)
+			o.Credentials = aws.NewCredentialsCache(roleProvider)
 		})
 	}
 

exporter/awskinesisexporter/exporter_test.go

@@ -46,6 +46,7 @@ func TestCreatingExporter(t *testing.T) {
 			conf: applyConfigChanges(func(conf *Config) {
 				conf.AWS.StreamName = "example-test"
 				conf.AWS.Region = "us-east-1"
+				conf.AWS.Role = "example-role"
 			}),
 			validateNew: func(tb testing.TB) func(conf aws.Config, opts ...func(*kinesis.Options)) *kinesis.Client {
 				return func(conf aws.Config, opts ...func(*kinesis.Options)) *kinesis.Client {