Refactor codebase, introduce relaymode package, update constants and improve consistency

- Refactor constant definitions and organization
- Clean up package level variables and functions
- Introduce new `relaymode` and `apitype` packages for constant definitions
- Refactor and simplify code in several packages including `openai`, `relay/channel/baidu`, `relay/util`, `relay/controller`, `relay/channeltype`
- Add helper functions in `relay/channeltype` package to convert channel type constants to corresponding API type constants
- Remove deprecated functions such as `ResponseText2Usage` from `relay/channel/openai/helper.go`
- Modify code in `relay/util/validation.go` and related files to use new `validator.ValidateTextRequest` function
- Rename `util` package to `relaymode` and update related imports in several packages

relay/adaptor/anthropic/model.go

@@ -0,0 +1,89 @@
+package anthropic
+
+// https://docs.anthropic.com/claude/reference/messages_post
+
+type Metadata struct {
+	UserId string `json:"user_id"`
+}
+
+type ImageSource struct {
+	Type      string `json:"type"`
+	MediaType string `json:"media_type"`
+	Data      string `json:"data"`
+}
+
+type Content struct {
+	Type   string       `json:"type"`
+	Text   string       `json:"text,omitempty"`
+	Source *ImageSource `json:"source,omitempty"`
+}
+
+type Message struct {
+	Role    string    `json:"role"`
+	Content []Content `json:"content"`
+}
+
+type Request struct {
+	Model         string    `json:"model"`
+	Messages      []Message `json:"messages"`
+	System        string    `json:"system,omitempty"`
+	MaxTokens     int       `json:"max_tokens,omitempty"`
+	StopSequences []string  `json:"stop_sequences,omitempty"`
+	Stream        bool      `json:"stream,omitempty"`
+	Temperature   float64   `json:"temperature,omitempty"`
+	TopP          float64   `json:"top_p,omitempty"`
+	TopK          int       `json:"top_k,omitempty"`
+	//Metadata    `json:"metadata,omitempty"`
+}
+
+type Usage struct {
+	InputTokens  int `json:"input_tokens"`
+	OutputTokens int `json:"output_tokens"`
+}
+
+type Error struct {
+	Type    string `json:"type"`
+	Message string `json:"message"`
+}
+
+type ResponseType string
+
+const (
+	TypeError        ResponseType = "error"
+	TypeStart        ResponseType = "message_start"
+	TypeContentStart ResponseType = "content_block_start"
+	TypeContent      ResponseType = "content_block_delta"
+	TypePing         ResponseType = "ping"
+	TypeContentStop  ResponseType = "content_block_stop"
+	TypeMessageDelta ResponseType = "message_delta"
+	TypeMessageStop  ResponseType = "message_stop"
+)
+
+// https://docs.anthropic.com/claude/reference/messages-streaming
+type Response struct {
+	Id           string    `json:"id"`
+	Type         string    `json:"type"`
+	Role         string    `json:"role"`
+	Content      []Content `json:"content"`
+	Model        string    `json:"model"`
+	StopReason   *string   `json:"stop_reason"`
+	StopSequence *string   `json:"stop_sequence"`
+	Usage        Usage     `json:"usage"`
+	Error        Error     `json:"error"`
+}
+
+type Delta struct {
+	Type         string  `json:"type"`
+	Text         string  `json:"text"`
+	StopReason   *string `json:"stop_reason"`
+	StopSequence *string `json:"stop_sequence"`
+}
+
+type StreamResponse struct {
+	Type         string    `json:"type"`
+	Message      *Response `json:"message"`
+	Index        int       `json:"index"`
+	ContentBlock *Content  `json:"content_block"`
+	Delta        *Delta    `json:"delta"`
+	Usage        *Usage    `json:"usage"`
+}