[TUBEMQ-482] Add offset query api

[gosonzhang]

1. add group offset query api

[codecov-io]

Codecov Report

Merging #371 (855f41e) into master (23cff5b) will decrease coverage by 0.03%.
The diff coverage is 0.00%.

@@             Coverage Diff             @@
##             master    #371      +/-   ##
===========================================
- Coverage      7.67%   7.63%   -0.04%     
  Complexity      468     468              
===========================================
  Files           261     263       +2     
  Lines         28500   28643     +143     
  Branches       4700    4720      +20     
===========================================
  Hits           2187    2187              
- Misses        25837   25980     +143     
  Partials        476     476              

Impacted Files	Coverage Δ	Complexity Δ
...e/tubemq/server/broker/metadata/TopicMetadata.java	17.22% <0.00%> (-1.15%)	5.00 <0.00> (ø)
...he/tubemq/server/broker/msgstore/MessageStore.java	0.00% <0.00%> (ø)	0.00 <0.00> (ø)
...mq/server/broker/msgstore/MessageStoreManager.java	0.00% <0.00%> (ø)	0.00 <0.00> (ø)
...emq/server/broker/offset/DefaultOffsetManager.java	0.00% <0.00%> (ø)	0.00 <0.00> (ø)
...he/tubemq/server/broker/utils/GroupOffsetInfo.java	0.00% <0.00%> (ø)	0.00 <0.00> (?)
.../tubemq/server/broker/utils/TopicPubStoreInfo.java	0.00% <0.00%> (ø)	0.00 <0.00> (?)
...e/tubemq/server/broker/web/BrokerAdminServlet.java	0.00% <0.00%> (ø)	0.00 <0.00> (ø)

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[lamberliu]

+1