Validator bonds contract first version

[ochaloup]

PR contains the code for the raw on-chain validator bonds program + some unit tests.

SDK, CLI, tests and functionality verification will be incoming in future code changes.

@janlegner this should be in a shape we talked about in our discussions and hopefully it stands for a functional design where only some details need to be adjusted.

[janlegner]

Few notes to keep in mind as per our discussion:

• readme with table of what stake_authority/withdraw_authority are at which stages
• withdrawer_authority -> withdraw_authority
• lockups - users can create arbitrary stake accounts (even with lockups), sdk must be prepared for that when showing total usable deposits
• deactivated accounts may change delegation when merged (e.g. with maliciously crafted stake account), double-check that we are ready for this when merging/dealing with deactivated accounts

[ochaloup]

@janlegner thanks a lot for the comments and the review.

Meanwhile I work on the base TS SDK calls and tests that I'm not putting to this PR and I add only changes particular to the contract itself.

• I renamed deposit_bond to fund_bond (the way how fund_settlement is named) and with that withdraw_deposit to claim_withdraw_request (I want to have the withdraw_request to be used as term for init, cancel and a obtain action of the withdrawal)
• I found an runtime issue with deserialization of vote account that was adjusted
• I think to have parameterized the amount of minimum stake. It was 1 SOL as constant but with incoming changes to Solana it makes sense to me to be configurable in Config.
• +1, reset stake means to activate the stake as well
• I bit hesitate to change the term withdrawer authority to withdraw authority. But I don't say I'm against. I would like just to double check. My initial attempt was to be consistent with stake account naming (https://github.com/solana-labs/solana/blob/v1.17.10/sdk/program/src/stake/state.rs#L279). I can see that the bot uses rather the withdraw authority term. So just to double check on intentions and naming terminology.
• that part with lockups is right and I'm aware that SDK needs to manage it. On rechecking this I changed the way how the lockup is checked. Custodian handling removed. It complicates the thing, it could be added later.
• thanks for noting on the merging of the deactivated stake accounts. The merge permits only to merge when the staker authorities matches and when the delegation matches. I recheck the other commands and updated to be aware of the different stake accounts can be provided maliciously.

[janlegner]

* I bit hesitate to change the term `withdrawer authority` to `withdraw authority`. But I don't say I'm against. I would like just to double check. My initial attempt was to be consistent with stake account naming (https://github.com/solana-labs/solana/blob/v1.17.10/sdk/program/src/stake/state.rs#L279). I can see that the bot uses rather the `withdraw authority` term. So just to double check on intentions and naming terminology.

My bad, I thought the withdraw authority is consistent with stake program but i was wrong

[janlegner]

we can merge this and continue work in consequent PRs