[v0.9] Remove penalties on recovery and on missed PoSt (FIP-0002)

[anorth]

Honest miners are sometimes disproportionately penalized for operational failures and network congestion by the high undeclared-fault penalty (aka SP) for missed Window PoSts. This change reduces those costs without sacrificing much of the incentive to maintain reliable storage.

Summary:

• Remove fee incurred when a sector is successfully recovered.
• Remove fee incurred by sectors faulted when a Window PoSt is missed.
• Update Sector Fault Fee (FF) to 3.51 days of expected block reward, for ongoing faults.

As a result of this, declaring faults in advance confers no advantage compared with skipping them at Window PoSt. The DeclareFaults method remains, but may be removed in the future.

This change is a demonstration of upcoming FIP-0002, which will describe more background and rationale.

Note that the new values are not directly tested in this PR. I intend to replicate on the v2 line and change all the tests there. UPDATE: see #1183

FYI @Stebalien @magik6k @whyrusleeping @zixuanzh @nicola

[codecov-commenter]

Codecov Report

Merging #1181 into release/v0.9 will decrease coverage by 0.0%.
The diff coverage is 76.1%.

@@              Coverage Diff               @@
##           release/v0.9   #1181     +/-   ##
==============================================
- Coverage          73.2%   73.2%   -0.1%     
==============================================
  Files                51      51             
  Lines              5450    5470     +20     
==============================================
+ Hits               3994    4006     +12     
- Misses              876     877      +1     
- Partials            580     587      +7     

[zixuanzh]

FIP-0002 Draft: https://github.com/filecoin-project/FIPs/blob/master/FIPS/fip-0002.md

[ZenGround0]

@lucaniz @irenegia I looked over this again and it appears to be correct. previouslyFaultPower already accounts for failedRecoveryPower (we only handle failedRecoveryPower separately in the previous version because we used to charge this power SP). Another way to put it, the value of deadline.FaultyPower.QA at line 1683 after processing deadline end = previouslyFaultPower - newFaultyPower

[ZenGround0]

This looks good