wire: omit the local package identifier if it matches the package name (google/go-cloud#385)

Fixes google/go-cloud#424

internal/wire/testdata/CopyOtherDecls/want/wire_gen.go

@@ -6,7 +6,7 @@
 package main
 
 import (
-	fmt "fmt"
+	"fmt"
 )
 
 // Injectors from foo.go:

internal/wire/testdata/ExportedValue/want/wire_gen.go

@@ -6,7 +6,7 @@
 package main
 
 import (
-	bar "example.com/bar"
+	"example.com/bar"
 )
 
 // Injectors from wire.go:

internal/wire/testdata/ExportedValueDifferentPackage/want/wire_gen.go

@@ -6,7 +6,7 @@
 package main
 
 import (
-	os "os"
+	"os"
 )
 
 // Injectors from wire.go:

internal/wire/testdata/ImportedInterfaceBinding/want/wire_gen.go

@@ -6,7 +6,7 @@
 package main
 
 import (
-	foo "example.com/foo"
+	"example.com/foo"
 )
 
 // Injectors from wire.go:

internal/wire/testdata/InterfaceValue/want/wire_gen.go

@@ -6,8 +6,8 @@
 package main
 
 import (
-	io "io"
-	strings "strings"
+	"io"
+	"strings"
 )
 
 // Injectors from wire.go:

internal/wire/testdata/MultipleSimilarPackages/want/wire_gen.go

@@ -6,10 +6,10 @@
 package main
 
 import (
-	bar "example.com/bar"
-	baz "example.com/baz"
-	foo "example.com/foo"
-	fmt "fmt"
+	"example.com/bar"
+	"example.com/baz"
+	"example.com/foo"
+	"fmt"
 )
 
 // Injectors from wire.go:

internal/wire/testdata/NamingWorstCaseAllInOne/want/wire_gen.go

@@ -7,9 +7,9 @@ package main
 
 import (
 	context2 "context"
-	fmt "fmt"
-	os "os"
-	reflect "reflect"
+	"fmt"
+	"os"
+	"reflect"
 )
 
 // Injectors from foo.go:

internal/wire/testdata/PkgImport/want/wire_gen.go

@@ -6,7 +6,7 @@
 package main
 
 import (
-	bar "example.com/bar"
+	"example.com/bar"
 )
 
 // Injectors from wire.go:

internal/wire/testdata/Vendor/want/wire_gen.go

@@ -6,7 +6,7 @@
 package main
 
 import (
-	bar "example.com/bar"
+	"example.com/bar"
 )
 
 // Injectors from wire.go: