Add methods toPrettyJsonString() and toSingleLineJsonString() to Schema

[Jackie-Jiang]

• For human-read API, use pretty string
• For other purpose, use compact single-line string

Fix the issue of storing pretty string in ZK (consume more space and less readable)

[codecov-io]

Codecov Report

Merging #3783 into master will increase coverage by 0.05%.
The diff coverage is 66.66%.

@@             Coverage Diff              @@
##             master    #3783      +/-   ##
============================================
+ Coverage     67.22%   67.28%   +0.05%     
  Complexity        4        4              
============================================
  Files          1027     1027              
  Lines         50812    50816       +4     
  Branches       7091     7091              
============================================
+ Hits          34159    34192      +33     
+ Misses        14312    14286      -26     
+ Partials       2341     2338       -3

Impacted Files	Coverage Δ	Complexity Δ
...org/apache/pinot/common/config/CombinedConfig.java	34.48% <0%> (-2.56%)	0 <0> (ø)
...not/controller/api/resources/PinotTableSchema.java	0% <0%> (ø)	0 <0> (ø)	⬇️
...main/java/org/apache/pinot/common/data/Schema.java	80.51% <100%> (+0.17%)	0 <0> (ø)	⬇️
...ava/org/apache/pinot/common/utils/SchemaUtils.java	9.85% <50%> (ø)	0 <0> (ø)	⬇️
...ller/api/resources/PinotSchemaRestletResource.java	40.57% <50%> (ø)	0 <0> (ø)	⬇️
...er/validation/BrokerResourceValidationManager.java	31.57% <0%> (-42.11%)	0% <0%> (ø)
...a/manager/realtime/RealtimeSegmentDataManager.java	75% <0%> (-25%)	0% <0%> (ø)
...egation/function/customobject/MinMaxRangePair.java	75.86% <0%> (-24.14%)	0% <0%> (ø)
...lix/EmptyBrokerOnlineOfflineStateModelFactory.java	86.66% <0%> (-13.34%)	0% <0%> (ø)
...impl/dictionary/DoubleOnHeapMutableDictionary.java	68.88% <0%> (-13.34%)	0% <0%> (ø)
... and 33 more

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[snleee]

Do we plan to do this for table config as well? Otherwise, LGTM

[sunithabeeram]

The impact of this change is unclear to me. Will any API responses be affected by this change? If so we should check backward compatibility implications.

[Jackie-Jiang]

@sunithabeeram We support both format, and it's mainly for saving space & readability.