Remove the dependency async-trait

[4t145]

Remove the dependency async-trait, for issue #20

Motivation and Context

How Has This Been Tested?

All the test passed

Breaking Changes

Exsited code need to remove the dependency async-trait and make their future return value Send.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation update

Checklist

• I have read the MCP Documentation
• My code follows the repository's style guidelines
• New and existing tests pass locally
• I have added appropriate error handling
• I have added or updated documentation as needed

Additional context

[cbrit]

@4t145 Could you fix the linter/test errors?

[4t145]

@4t145 Could you fix the linter/test errors?

I didn't realize that you may need to create boxed dyn client here. So this is not good to simply remove all #[async-trait]. Maybe we should rethink about this pr?

[4t145]

I would like to close this pr temporarily, and discussions can be continued on #20.