tlv/internal: add new internal package for generating TLV type structs

In this commit, we add some new code generation to the codebase. As
we'll see in a future commit, this'll allow us to create a new Record[T,
V] type, where T is actually a concrete _struct_ that implements a
special interface that deems it as a valid TLV type.

tlv/internal/gen/gen_tlv_types.go

@@ -0,0 +1,59 @@
+package main
+
+import (
+	"bytes"
+	"flag"
+	"os"
+	"text/template"
+)
+
+const (
+	numberOfTypes     = 100
+	defaultOutputFile = "tlv_types_generated.go"
+)
+
+const typeCodeTemplate = `// Code generated by tlv/internal/gen; DO NOT EDIT.
+
+package tlv
+
+{{- range $index, $element := . }}
+
+type tlvType{{ $index }} struct{}
+
+func (t *tlvType{{ $index }}) typeVal() Type {
+	return {{ $index }}
+}
+
+type TlvType{{ $index }} = *tlvType{{ $index }}
+{{- end }}
+`
+
+func main() {
+	// Create a slice of items that the template can range over.
+	var items []struct{}
+	for i := uint16(0); i <= numberOfTypes; i++ {
+		items = append(items, struct{}{})
+	}
+
+	tpl, err := template.New("tlv").Parse(typeCodeTemplate)
+	if err != nil {
+		panic(err)
+	}
+
+	// Execute the template
+	var out bytes.Buffer
+	err = tpl.Execute(&out, items)
+	if err != nil {
+		panic(err)
+	}
+
+	outputFile := flag.String(
+		"o", defaultOutputFile, "Output file for generated code",
+	)
+	flag.Parse()
+
+	err = os.WriteFile(*outputFile, out.Bytes(), 0644)
+	if err != nil {
+		panic(err)
+	}
+}