Support more different types of withdraw stake

[NingLin-P]

This PR supports more different types of withdraw stakes:

• All, withdraw all the known stake
• Percent, withdraw a given percentage of the known stake
• Stake, withdraw a given amount of stake (i.e. balance)
  • The stake is calculated by the share price at this instant, it may not be accurate and may withdraw a bit more stake if there is reward happen later in this epoch
• Share, withdraw a given amount of share, same as the current withdraw_stake

NOTE: the deposit that happens in the current epoch may not be withdrawn until the current epoch ends and the above calculation doesn't include such a deposit.

cc @marc-aurele-besner

Code contributor checklist:

• [x] I have read, understood and followed contributing guide

[NingLin-P]

Plz take a look @dastansam @dariolina thanks!