Added Participation Key Expiration Check (algorand#2924)

## Summary

Resolves algorand#2738

Adds the following:

- consensus.go: Adds the default MaxExpiredAccountsToProcess value for
  the new consensus protocol
- block.go: Adds necessary block header entries
- eval.go: Scans for expired accounts, modifies them to be offline and adds
  validation for this use case
- eval_test.go: Basic unit tests
- participationExpiration_test.go: Added e2e tests that verify that
  different consensus protocols behave differently

## Test Plan

Unit test and e2e tests added

Author: AlgoStephenAkiki

agreement/msgp_gen.go

@@ -391,6 +391,10 @@ type ConsensusParams struct {
 	EnableKeyregCoherencyCheck bool
 
 	EnableExtraPagesOnAppUpdate bool
+
+	// MaxProposedExpiredOnlineAccounts is the maximum number of online accounts, which need
+	// to be taken offline, that would be proposed to be taken offline.
+	MaxProposedExpiredOnlineAccounts int
 }
 
 // PaysetCommitType enumerates possible ways for the block header to commit to
@@ -465,6 +469,10 @@ var MaxExtraAppProgramLen int
 //supported supported by any of the consensus protocols. used for decoding purposes.
 var MaxAvailableAppProgramLen int
 
+// MaxProposedExpiredOnlineAccounts is the maximum number of online accounts, which need
+// to be taken offline, that would be proposed to be taken offline.
+var MaxProposedExpiredOnlineAccounts int
+
 func checkSetMax(value int, curMax *int) {
 	if value > *curMax {
 		*curMax = value
@@ -501,6 +509,7 @@ func checkSetAllocBounds(p ConsensusParams) {
 	// Its value is much larger than any possible reasonable MaxLogCalls value in future
 	checkSetMax(p.MaxAppProgramLen, &MaxLogCalls)
 	checkSetMax(p.MaxInnerTransactions, &MaxInnerTransactions)
+	checkSetMax(p.MaxProposedExpiredOnlineAccounts, &MaxProposedExpiredOnlineAccounts)
 }
 
 // SaveConfigurableConsensus saves the configurable protocols file to the provided data directory.
@@ -1045,6 +1054,8 @@ func initConsensusProtocols() {
 	// Enable TEAL 6 / AVM 1.1
 	vFuture.LogicSigVersion = 6
 
+	vFuture.MaxProposedExpiredOnlineAccounts = 32
+
 	Consensus[protocol.ConsensusFuture] = vFuture
 }
 

config/consensus.go

@@ -397,6 +397,16 @@ func MakeAccountData(status Status, algos MicroAlgos) AccountData {
 	return AccountData{Status: status, MicroAlgos: algos}
 }
 
+// ClearOnlineState resets the account's fields to indicate that the account is an offline account
+func (u *AccountData) ClearOnlineState() {
+	u.Status = Offline
+	u.VoteFirstValid = Round(0)
+	u.VoteLastValid = Round(0)
+	u.VoteKeyDilution = 0
+	u.VoteID = crypto.OneTimeSignatureVerifier{}
+	u.SelectionID = crypto.VRFVerifier{}
+}
+
 // Money returns the amount of MicroAlgos associated with the user's account
 func (u AccountData) Money(proto config.ConsensusParams, rewardsLevel uint64) (money MicroAlgos, rewards MicroAlgos) {
 	e := u.WithUpdatedRewards(proto, rewardsLevel)

data/basics/userBalance.go

@@ -125,6 +125,21 @@ type (
 		// for multiple types of certs.
 		//msgp:sort protocol.CompactCertType protocol.SortCompactCertType
 		CompactCert map[protocol.CompactCertType]CompactCertState `codec:"cc,allocbound=protocol.NumCompactCertTypes"`
+
+		// ParticipationUpdates contains the information needed to mark
+		// certain accounts offline because their participation keys expired
+		ParticipationUpdates
+	}
+
+	// ParticipationUpdates represents participation account data that
+	// needs to be checked/acted on by the network
+	ParticipationUpdates struct {
+		_struct struct{} `codec:",omitempty,omitemptyarray"`
+
+		// ExpiredParticipationAccounts contains a list of online accounts
+		// that needs to be converted to offline since their
+		// participation key expired.
+		ExpiredParticipationAccounts []basics.Address `codec:"partupdrmv,allocbound=config.MaxProposedExpiredOnlineAccounts"`
 	}
 
 	// RewardsState represents the global parameters controlling the rate