Add handleUndeleteRequest method to AmbryRequests

[justinlin-linkedin]

Adding handleUndeleteRequest method to AmbryRequests class to handle undelete requests from ambry-frontend.
Add unit test and integration test for handleUndeleteRequest
Change some of the Store implementation in replication test, but since we are not change replication logic for undelete now, we don't change those implementation to support undelete for now.

[codecov-io]

Codecov Report

Merging #1379 into master will increase coverage by 0.1%.
The diff coverage is 100%.

@@             Coverage Diff             @@
##             master    #1379     +/-   ##
===========================================
+ Coverage     72.34%   72.45%   +0.1%     
- Complexity     6870     6881     +11     
===========================================
  Files           496      496             
  Lines         38854    38933     +79     
  Branches       4940     4947      +7     
===========================================
+ Hits          28109    28207     +98     
+ Misses         9386     9368     -18     
+ Partials       1359     1358      -1

Impacted Files	Coverage Δ	Complexity Δ
...va/com.github.ambry.protocol/UndeleteResponse.java	78.26% <100%> (+2.65%)	15 <3> (+2)	⬆️
...a/com.github.ambry.server/AmbryServerRequests.java	94.13% <100%> (+0.05%)	78 <0> (+2)	⬆️
.../java/com.github.ambry.protocol/AmbryRequests.java	85.68% <100%> (+1.61%)	77 <8> (+9)	⬆️
...in/java/com.github.ambry.commons/ErrorMapping.java	82.75% <100%> (+2.75%)	3 <0> (ø)	⬇️
...ain/java/com.github.ambry/config/ServerConfig.java	100% <100%> (ø)	1 <0> (ø)	⬇️
...n/java/com.github.ambry.commons/ServerMetrics.java	100% <100%> (ø)	15 <0> (ø)	⬇️
.../java/com.github.ambry/server/ServerErrorCode.java	100% <100%> (ø)	1 <0> (ø)	⬇️
.../main/java/com.github.ambry.store/ScanResults.java	81.25% <0%> (-1.57%)	16% <0%> (-1%)
...in/java/com.github.ambry.store/BlobStoreStats.java	71.04% <0%> (-1.05%)	104% <0%> (ø)
...main/java/com.github.ambry.store/IndexSegment.java	87.16% <0%> (-0.37%)	130% <0%> (-2%)
... and 9 more

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[zzmao]

Some comments left.

[jsjtzyy]

just one minor comment left