The lite-core module decouples ZooKeeper

[mytang0]

Fixes #2183 .

Changes proposed in this pull request:

The elasticjob-lite-core module decouples ZooKeeper, introduce the implementation of the on-demand registration center when using it.

[codecov-commenter]

Codecov Report

Merging #2182 (aea9c7f) into master (bf9bf75) will not change coverage. The diff coverage is 81.81%.

@@            Coverage Diff            @@
##             master    #2182   +/-   ##
=========================================
  Coverage     84.61%   84.61%           
- Complexity     1916     1917    +1     
=========================================
  Files           286      287    +1     
  Lines          6279     6279           
  Branches        695      692    -3     
=========================================
  Hits           5313     5313           
- Misses          646      648    +2     
+ Partials        320      318    -2     

Impacted Files	Coverage Δ
...sticjob/lite/api/registry/JobInstanceRegistry.java	41.37% <0.00%> (ø)
...ite/internal/listener/ListenerNotifierManager.java	89.47% <ø> (ø)
...ere/elasticjob/lite/internal/util/ThreadUtils.java	70.00% <70.00%> (ø)
...ticjob/lite/internal/snapshot/SnapshotService.java	89.70% <100.00%> (+3.80%)	:arrow_up:
...ite/internal/election/ElectionListenerManager.java	91.66% <0.00%> (-4.17%)	:arrow_down:

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[mytang0]

Please take a look @TeslaCN