Feature/support conditional tool calling

[ZackYule]

Description

Builded a FSM with FunctionToolState and tools_space to support conditional tool calling.

Motivation and Context

close #951

• I have raised an issue to propose this change (required for new features and bug fixes)

Types of changes

What types of changes does your code introduce? Put an x in all the boxes that apply:

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds core functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation (update in the documentation)
• Example (update in the folder of example)

Implemented Tasks

• Complete the basic structure.
• Creating a single agent demo.
• Configuring the TaskManager through agents.
• Replace with more appropriate variable names.

Checklist

Go over all the following points, and put an x in all the boxes that apply.
If you are unsure about any of these, don't hesitate to ask. We are here to help!

• I have read the CONTRIBUTION guide. (required)
• My change requires a change to the documentation.
• I have updated the tests accordingly. (required for a bug fix or a new feature)
• I have updated the documentation accordingly.

[ZackYule]

Related to issue #951

[ZackYule]

I think the root_task should be removed from the TaskManager, because according to its design, it can add tasks and sort them without setting all tasks as sub-tasks of a root_task. There is also no special handling for root_task. So I want to know if removing the root_task is appropriate, as it would make the code of support conditional tool calling more elegant. @yiyiyi0817 @zhiyu-01

[Wendong-Fan]

Hey @ZackYule , this PR need to be cleaned for further code review, how it includes some change from former commited PR, also could you fix the conflict with master branch?