[Raft] make me crazy

[critical27]

Origins from and rely on #3031, some code may be conflicted as well, wait that merge first.

Change notes:

1. Cherry-pick Raft problem #2483 and apply to 2.0
2. Since Raft problem #2483, we could remove the weird code in Host (magic code), for example:

    if (logId <= lastLogIdSent_) {
      LOG(INFO) << idStr_ << "The log " << logId << " has been sended"
                << ", lastLogIdSent " << lastLogIdSent_;
      cpp2::AppendLogResponse r;
      r.set_error_code(cpp2::ErrorCode::SUCCEEDED);
      return r;
    }

and many

              } else if (self->lastLogIdSent_ == resp.get_last_log_id()) {
                VLOG(2) << self->idStr_ << "We send nothing in the last request"
                        << ", so we don't send the same logs again";
                self->lastLogIdSent_ = resp.get_last_log_id();
                self->lastLogTermSent_ = resp.get_last_log_term();
                self->followerCommittedLogId_ = resp.get_committed_log_id();
                cpp2::AppendLogResponse r;
                r.set_error_code(cpp2::ErrorCode::SUCCEEDED);
                self->setResponse(r);

3. We can't send the wals after snapshot, because if all the wals after snapshot has been sent, and we reboot during the snapshot is sending, the partition could be elected as leader (only check lastLogId). Just delete these logic in the code, follower only can append more logs after snapshot is received.
4. Fix a partition is reset way more than expected times during waiting for snapshot.
5. Many logic in Host has been unified. I will describe the invariant later.

Todo:

1. Follow-up of separate thenValue/thenError when rpc fail to handle timeout #3031, add a back-off time when leader send logs timeout, to avoid make thing worse.
2. I tried to use different eventbase for each Host when appendLogs, but it seems failed (crashed a lot), still working on it.

[critical27]

Close #3018, #3019, #3147

[kikimo]

LGTM

[kikimo]

LGTM

[codecov-commenter]

Codecov Report

Merging #3172 (b170bf9) into master (7f711bb) will increase coverage by 0.02%.
The diff coverage is 78.73%.

@@            Coverage Diff             @@
##           master    #3172      +/-   ##
==========================================
+ Coverage   85.20%   85.23%   +0.02%     
==========================================
  Files        1304     1288      -16     
  Lines      119897   119876      -21     
==========================================
+ Hits       102164   102173       +9     
+ Misses      17733    17703      -30     

Impacted Files	Coverage Δ
src/clients/meta/MetaClient.cpp	76.40% <ø> (+1.13%)	⬆️
src/clients/meta/MetaClient.h	95.65% <ø> (ø)
src/common/datatypes/Edge.h	100.00% <ø> (ø)
src/common/expression/PathBuildExpression.h	100.00% <ø> (ø)
...c/common/expression/test/ExpressionContextMock.cpp	100.00% <ø> (ø)
src/common/utils/Types.h	100.00% <ø> (ø)
src/graph/context/Iterator.h	73.79% <ø> (-0.69%)	⬇️
src/graph/executor/admin/SubmitJobExecutor.h	100.00% <ø> (ø)
src/graph/planner/match/MatchClausePlanner.h	100.00% <ø> (ø)
src/graph/planner/match/MatchSolver.cpp	47.05% <0.00%> (-50.00%)	⬇️
... and 149 more

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