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/ollama/model.go

@@ -0,0 +1,47 @@
+package ollama
+
+type Options struct {
+	Seed             int     `json:"seed,omitempty"`
+	Temperature      float64 `json:"temperature,omitempty"`
+	TopK             int     `json:"top_k,omitempty"`
+	TopP             float64 `json:"top_p,omitempty"`
+	FrequencyPenalty float64 `json:"frequency_penalty,omitempty"`
+	PresencePenalty  float64 `json:"presence_penalty,omitempty"`
+}
+
+type Message struct {
+	Role    string   `json:"role,omitempty"`
+	Content string   `json:"content,omitempty"`
+	Images  []string `json:"images,omitempty"`
+}
+
+type ChatRequest struct {
+	Model    string    `json:"model,omitempty"`
+	Messages []Message `json:"messages,omitempty"`
+	Stream   bool      `json:"stream"`
+	Options  *Options  `json:"options,omitempty"`
+}
+
+type ChatResponse struct {
+	Model           string  `json:"model,omitempty"`
+	CreatedAt       string  `json:"created_at,omitempty"`
+	Message         Message `json:"message,omitempty"`
+	Response        string  `json:"response,omitempty"` // for stream response
+	Done            bool    `json:"done,omitempty"`
+	TotalDuration   int     `json:"total_duration,omitempty"`
+	LoadDuration    int     `json:"load_duration,omitempty"`
+	PromptEvalCount int     `json:"prompt_eval_count,omitempty"`
+	EvalCount       int     `json:"eval_count,omitempty"`
+	EvalDuration    int     `json:"eval_duration,omitempty"`
+	Error           string  `json:"error,omitempty"`
+}
+
+type EmbeddingRequest struct {
+	Model  string `json:"model"`
+	Prompt string `json:"prompt"`
+}
+
+type EmbeddingResponse struct {
+	Error     string    `json:"error,omitempty"`
+	Embedding []float64 `json:"embedding,omitempty"`
+}