go: include vendored modules

RHEL requires the source code for dependencies to be included in the
srpm. The spec file already expects that, but we've only included the
vendored modules (i.e., the `vendor` directory) in the `rhel-8.2.`
branch. Move vendoring to master, so that we can build RHEL packages
from it as well.

This commit is the result of running `go mod vendor`, which includes the
vendored sources and updates go.mod and go.sum files.

Fedora requires the opposite: dependencies should not be vendored. The
spec file already ignores the `vendor` directory by default.

vendor/github.com/aws/aws-sdk-go/private/protocol/restxml/restxml.go

@@ -0,0 +1,79 @@
+// Package restxml provides RESTful XML serialization of AWS
+// requests and responses.
+package restxml
+
+//go:generate go run -tags codegen ../../../models/protocol_tests/generate.go ../../../models/protocol_tests/input/rest-xml.json build_test.go
+//go:generate go run -tags codegen ../../../models/protocol_tests/generate.go ../../../models/protocol_tests/output/rest-xml.json unmarshal_test.go
+
+import (
+	"bytes"
+	"encoding/xml"
+
+	"github.com/aws/aws-sdk-go/aws/awserr"
+	"github.com/aws/aws-sdk-go/aws/request"
+	"github.com/aws/aws-sdk-go/private/protocol/query"
+	"github.com/aws/aws-sdk-go/private/protocol/rest"
+	"github.com/aws/aws-sdk-go/private/protocol/xml/xmlutil"
+)
+
+// BuildHandler is a named request handler for building restxml protocol requests
+var BuildHandler = request.NamedHandler{Name: "awssdk.restxml.Build", Fn: Build}
+
+// UnmarshalHandler is a named request handler for unmarshaling restxml protocol requests
+var UnmarshalHandler = request.NamedHandler{Name: "awssdk.restxml.Unmarshal", Fn: Unmarshal}
+
+// UnmarshalMetaHandler is a named request handler for unmarshaling restxml protocol request metadata
+var UnmarshalMetaHandler = request.NamedHandler{Name: "awssdk.restxml.UnmarshalMeta", Fn: UnmarshalMeta}
+
+// UnmarshalErrorHandler is a named request handler for unmarshaling restxml protocol request errors
+var UnmarshalErrorHandler = request.NamedHandler{Name: "awssdk.restxml.UnmarshalError", Fn: UnmarshalError}
+
+// Build builds a request payload for the REST XML protocol.
+func Build(r *request.Request) {
+	rest.Build(r)
+
+	if t := rest.PayloadType(r.Params); t == "structure" || t == "" {
+		var buf bytes.Buffer
+		err := xmlutil.BuildXML(r.Params, xml.NewEncoder(&buf))
+		if err != nil {
+			r.Error = awserr.NewRequestFailure(
+				awserr.New(request.ErrCodeSerialization,
+					"failed to encode rest XML request", err),
+				0,
+				r.RequestID,
+			)
+			return
+		}
+		r.SetBufferBody(buf.Bytes())
+	}
+}
+
+// Unmarshal unmarshals a payload response for the REST XML protocol.
+func Unmarshal(r *request.Request) {
+	if t := rest.PayloadType(r.Data); t == "structure" || t == "" {
+		defer r.HTTPResponse.Body.Close()
+		decoder := xml.NewDecoder(r.HTTPResponse.Body)
+		err := xmlutil.UnmarshalXML(r.Data, decoder, "")
+		if err != nil {
+			r.Error = awserr.NewRequestFailure(
+				awserr.New(request.ErrCodeSerialization,
+					"failed to decode REST XML response", err),
+				r.HTTPResponse.StatusCode,
+				r.RequestID,
+			)
+			return
+		}
+	} else {
+		rest.Unmarshal(r)
+	}
+}
+
+// UnmarshalMeta unmarshals response headers for the REST XML protocol.
+func UnmarshalMeta(r *request.Request) {
+	rest.UnmarshalMeta(r)
+}
+
+// UnmarshalError unmarshals a response error for the REST XML protocol.
+func UnmarshalError(r *request.Request) {
+	query.UnmarshalError(r)
+}