stake-program: MoveStake and MoveLamports

[2501babe]

Problem

due to split destinations requiring rent-exemption, there isnt a good way to move value between stake accounts without holding Withdrawer authority, because split/merge cycles require new lamports to fund split when then results in unreclaimable undelegated lamports accumulating in merge destinations

Summary of Changes

we implement two new instructions, MoveStake and MoveLamports, which move stake and lamports between stake accounts with the same authorized/lockup, using Staker authority. further detail can be found in (simd148)[https://github.com/solana-foundation/solana-improvement-documents/pull/148], which this intends to implement

Feature Gate Issue: #1610

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 13.15789% with 165 lines in your changes are missing coverage. Please review.

Project coverage is 82.7%. Comparing base (20ee70c) to head (06c50ca).
Report is 55 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff            @@
##           master    #1415     +/-   ##
=========================================
- Coverage    82.7%    82.7%   -0.1%     
=========================================
  Files         871      871             
  Lines      369894   370084    +190     
=========================================
+ Hits       306158   306222     +64     
- Misses      63736    63862    +126     

[2501babe]

note to self this should be done except i need to make and put the feature gate issue in the feature text. i need to do a test run with a panic in the new tests first tho to make sure they actually run

[2501babe]

ok! my last force push was just to add instruction descriptions and delete some dead test code, previously it passed ci so this version should be final

ive split the pr into five commits for ease of reviewing:

• 6105c77: this is the most important one and contains the full impl of the new instructions
• 316215e: this just adds the instructions to transaction-status
• 2b24676: this adds the instruction to a few existing smoke tests in stake_instruction.rs
• a8e39ad: this wraps the instruction in a feature gate, using the same pattern as redelegate
• 1871f45: this is all the new tests for the new instruction, including the neostake test helpers needed to run them. worth skimming but this is the bulk of the new lines of code

[joncinque]

Really great work! The core logic is sound, and most of my comments are minor

[joncinque]

nit: not really important, but typically a helper struct is preferable to a 3-tuple

[2501babe]

note to future reviewers that 6105c77 is functionally identical to the tip of the branch but there was a structural change in a later commit, but all the important changes are in stake_instruction.rs, stake_state.rs, and stake/instruction.rs, and total ~400 lines, the other ~1500 are just tests and transaction parser code

[CriesofCarrots]

I haven't looked at stake-tests at all yet, but here's a first set of comments.