chore: support (u)int(8|16) fields ans slices, fix map issues,

This commit does several things:
- Adds support for (u)int(8|16) fields and slices. Any such type (except for []uint8 and [n]uint8) will be encoded as protobuf fixed32
- Refactor unmarshal.go
- Disallow encoding of maps with complex keys
- Disallow encoding of maps with repeated values
- Check pointer to slices in slices elements
- Support empty structs
- Arrays of complex types cannot be decoded for now
- Other small fixes

Signed-off-by: Dmitriy Matrenichev <dmitry.matrenichev@siderolabs.com>

.dockerignore

@@ -1,10 +1,9 @@
 # THIS FILE WAS AUTOMATICALLY GENERATED, PLEASE DO NOT EDIT.
 #
-# Generated on 2022-08-04T13:22:07Z by kres latest.
+# Generated on 2022-08-09T01:20:13Z by kres latest.
 
 **
 !messages
-!array_test.go
 !benchmarks_test.go
 !example_test.go
 !field_test.go
@@ -17,6 +16,8 @@
 !person_test.go
 !predefined_types.go
 !protobuf_test.go
+!scanner.go
+!slice_test.go
 !type_cache.go
 !unmarshal.go
 !unmarshal_fastpath.go

Dockerfile

@@ -2,7 +2,7 @@
 
 # THIS FILE WAS AUTOMATICALLY GENERATED, PLEASE DO NOT EDIT.
 #
-# Generated on 2022-08-04T13:22:07Z by kres latest.
+# Generated on 2022-08-09T01:20:13Z by kres latest.
 
 ARG TOOLCHAIN
 
@@ -49,7 +49,6 @@ COPY ./go.sum .
 RUN --mount=type=cache,target=/go/pkg go mod download
 RUN --mount=type=cache,target=/go/pkg go mod verify
 COPY ./messages ./messages
-COPY ./array_test.go ./array_test.go
 COPY ./benchmarks_test.go ./benchmarks_test.go
 COPY ./example_test.go ./example_test.go
 COPY ./field_test.go ./field_test.go
@@ -62,6 +61,8 @@ COPY ./marshal_test.go ./marshal_test.go
 COPY ./person_test.go ./person_test.go
 COPY ./predefined_types.go ./predefined_types.go
 COPY ./protobuf_test.go ./protobuf_test.go
+COPY ./scanner.go ./scanner.go
+COPY ./slice_test.go ./slice_test.go
 COPY ./type_cache.go ./type_cache.go
 COPY ./unmarshal.go ./unmarshal.go
 COPY ./unmarshal_fastpath.go ./unmarshal_fastpath.go

field_test.go

@@ -14,7 +14,7 @@ import (
 	"github.com/siderolabs/protoenc"
 )
 
-func TestEncodeNested(t *testing.T) {
+func TestStructFields_EmbedStruct(t *testing.T) {
 	t.Parallel()
 
 	s := &StructWithEmbed{
@@ -65,7 +65,7 @@ type EmbedStruct struct {
 	C int32 `protobuf:"11"`
 }
 
-func TestDuplicateIDNotAllowed(t *testing.T) {
+func TestStructFields_DuplicateIDNotAllowed(t *testing.T) {
 	t.Parallel()
 
 	v := reflect.TypeOf(&StructWithDuplicates{})