[Raft] fix some remaining problems after pre-vote merged

[critical27]

I am reviewing current implementation, some issues are found:

1. We didn't save the info of voting for myself when start formal election, which could lead to split brain:
   • There are ABCDE 5 replicas, and BC vote for A.
   • If A does not voted itself, another host could be the leader, for example, E could be the leader with votes from ADE.
2. [Raft] Add prevote to make it better #3322 has missed one rollback, leader will check whether term/role changed after we get AppendLogResponse, if failed, we need to rollback, otherwise, we can't write any logs to wal since lastLogId_ != wal_->lastLogId().
3. When we start up, if lastLogId_ < committedLogId_, only lastLogId_ is set to committedLogId_.

And some minor changes, set leader_ whenever term changed, this is a prepare for later AppendLogs refactor.

[codecov-commenter]

Codecov Report

Merging #3415 (b889c81) into master (d6f83f3) will decrease coverage by 7.43%.
The diff coverage is 96.22%.

@@            Coverage Diff             @@
##           master    #3415      +/-   ##
==========================================
- Coverage   85.24%   77.80%   -7.44%     
==========================================
  Files        1278     1278              
  Lines      119200   119289      +89     
==========================================
- Hits       101608    92817    -8791     
- Misses      17592    26472    +8880     

Impacted Files	Coverage Δ
src/common/utils/NebulaKeyUtils.h	80.68% <ø> (ø)
src/common/utils/Types.h	100.00% <ø> (ø)
src/kvstore/raftex/RaftPart.cpp	72.35% <83.33%> (+0.81%)	⬆️
src/storage/exec/GetPropNode.h	89.55% <87.50%> (-0.45%)	⬇️
src/common/memory/MemoryUtils.cpp	93.33% <100.00%> (+0.65%)	⬆️
src/common/utils/MetaKeyUtils.cpp	82.15% <100.00%> (+0.78%)	⬆️
src/common/utils/NebulaKeyUtils.cpp	94.51% <100.00%> (+0.31%)	⬆️
src/common/utils/test/MetaKeyUtilsTest.cpp	94.63% <100.00%> (+0.30%)	⬆️
src/kvstore/raftex/test/RaftCase.cpp	71.12% <100.00%> (ø)
src/kvstore/test/DiskManagerTest.cpp	99.19% <100.00%> (+0.21%)	⬆️
... and 295 more

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[panda-sheep]

Good job!

[kikimo]

LGTM, I'll do more test together with the following raft pr.