Develop the test code of stake&unstake part in LiquidStaking2.0

[mclyk]

Motivation

While finishing the logic about #353 Should start to develop test code.

Suggested Solution develop test code in LiquidStaking

• [x] initial mock.rs and test.rs
• [ ] stake call test
• [ ] unstake call test
• [ ] claim call test

[mclyk]

close this issue due to new design: https://github.com/parallel-finance/parallel/issues/353#issuecomment-900080535