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>

uv.lock

@@ -3952,6 +3952,18 @@ wheels = [
     { url = "https://mirrors.aliyun.com/pypi/packages/88/5f/e351af9a41f866ac3f1fac4ca0613908d9a41741cfcf2228f4ad853b697d/pluggy-1.5.0-py3-none-any.whl", hash = "sha256:44e1ad92c8ca002de6377e165f3e0f1be63266ab4d554740532335b9d75ea669" },
 ]
 
+[[package]]
+name = "pluginlib"
+version = "0.9.4"
+source = { registry = "https://mirrors.aliyun.com/pypi/simple" }
+dependencies = [
+    { name = "setuptools" },
+]
+sdist = { url = "https://mirrors.aliyun.com/pypi/packages/58/38/ca974ba2d8ccc7954d8ccb0394cce184ac6269bd1fbfe06f70a0da3c8946/pluginlib-0.9.4.tar.gz", hash = "sha256:88727037138f759a3952f6391ae3751536f04ad8be6023607620ea49695a3a83" }
+wheels = [
+    { url = "https://mirrors.aliyun.com/pypi/packages/b0/b5/c869b3d2ed1613afeb02c635be11f5d35fa5b2b665f4d059cfe5b8e82941/pluginlib-0.9.4-py2.py3-none-any.whl", hash = "sha256:d4cfb7d74a6d2454e256b6512fbc4bc2dd7620cb7764feb67331ef56ce4b33f2" },
+]
+
 [[package]]
 name = "polars-lts-cpu"
 version = "1.9.0"
@@ -4872,6 +4884,7 @@ dependencies = [
     { name = "pdfplumber" },
     { name = "peewee" },
     { name = "pillow" },
+    { name = "pluginlib" },
     { name = "protobuf" },
     { name = "psycopg2-binary" },
     { name = "pyclipper" },
@@ -5009,6 +5022,7 @@ requires-dist = [
     { name = "pdfplumber", specifier = "==0.10.4" },
     { name = "peewee", specifier = "==3.17.1" },
     { name = "pillow", specifier = "==10.4.0" },
+    { name = "pluginlib", specifier = "==0.9.4" },
     { name = "protobuf", specifier = "==5.27.2" },
     { name = "psycopg2-binary", specifier = "==2.9.9" },
     { name = "pyclipper", specifier = "==1.3.0.post5" },