Feat: Support tool calling in Generate component (#7572)

### What problem does this PR solve?

Hello, our use case requires LLM agent to invoke some tools, so I made a
simple implementation here.

This PR does two things:

1. A simple plugin mechanism based on `pluginlib`:

This mechanism lives in the `plugin` directory. It will only load
plugins from `plugin/embedded_plugins` for now.

A sample plugin `bad_calculator.py` is placed in
`plugin/embedded_plugins/llm_tools`, it accepts two numbers `a` and `b`,
then give a wrong result `a + b + 100`.

In the future, it can load plugins from external location with little
code change.

Plugins are divided into different types. The only plugin type supported
in this PR is `llm_tools`, which must implement the `LLMToolPlugin`
class in the `plugin/llm_tool_plugin.py`.
More plugin types can be added in the future.

2. A tool selector in the `Generate` component:

Added a tool selector to select one or more tools for LLM:


![image](https://github.com/user-attachments/assets/74a21fdf-9333-4175-991b-43df6524c5dc)

And with the `bad_calculator` tool, it results this with the `qwen-max`
model:


![image](https://github.com/user-attachments/assets/93aff9c4-8550-414a-90a2-1a15a5249d94)


### Type of change

- [ ] Bug Fix (non-breaking change which fixes an issue)
- [x] New Feature (non-breaking change which adds functionality)
- [ ] Documentation Update
- [ ] Refactoring
- [ ] Performance Improvement
- [ ] Other (please describe):

Co-authored-by: Yingfeng <yingfeng.zhang@gmail.com>

web/src/components/llm-select/index.tsx

@@ -11,19 +11,31 @@ import { Select, SelectTrigger, SelectValue } from '../ui/select';
 interface IProps {
   id?: string;
   value?: string;
-  onChange?: (value: string) => void;
+  onInitialValue?: (value: string, option: any) => void;
+  onChange?: (value: string, option: any) => void;
   disabled?: boolean;
 }
 
-const LLMSelect = ({ id, value, onChange, disabled }: IProps) => {
+const LLMSelect = ({ id, value, onInitialValue, onChange, disabled }: IProps) => {
   const modelOptions = useComposeLlmOptionsByModelTypes([
     LlmModelType.Chat,
     LlmModelType.Image2text,
   ]);
 
+  if (onInitialValue && value) {
+    for (const modelOption of modelOptions) {
+      for (const option of modelOption.options) {
+        if (option.value === value) {
+          onInitialValue(value, option);
+          break;
+        }
+      }
+    }
+  }  
+
   const content = (
     <div style={{ width: 400 }}>
-      <LlmSettingItems
+      <LlmSettingItems onChange={onChange}
         formItemLayout={{ labelCol: { span: 10 }, wrapperCol: { span: 14 } }}
       ></LlmSettingItems>
     </div>