[serving] support load multiple version of a model on the same endpoint

[frankfliu]

• [serving] Remove GpuAssignmentStrategy.java
• [serving] support load multiple version of a model on the same endpoint

Description

Brief description of what this PR is about

• If this change is a backward incompatible change, why must this change be made?
• Interesting edge cases to note here

[codecov-commenter]

Codecov Report

Merging #1052 (584f758) into master (3b88cf9) will decrease coverage by 0.09%.
The diff coverage is 61.17%.

@@             Coverage Diff              @@
##             master    #1052      +/-   ##
============================================
- Coverage     70.12%   70.02%   -0.10%     
- Complexity     5197     5216      +19     
============================================
  Files           509      510       +1     
  Lines         23147    23250     +103     
  Branches       2455     2489      +34     
============================================
+ Hits          16232    16281      +49     
- Misses         5605     5643      +38     
- Partials       1310     1326      +16     

Impacted Files	Coverage Δ
.../java/ai/djl/repository/RepositoryFactoryImpl.java	76.74% <0.00%> (-1.83%)	⬇️
...ing/src/main/java/ai/djl/serving/wlm/Endpoint.java	42.22% <42.22%> (ø)
...ng/src/main/java/ai/djl/serving/wlm/ModelInfo.java	77.19% <60.00%> (-3.51%)	⬇️
...a/ai/djl/serving/http/InferenceRequestHandler.java	52.12% <61.11%> (+0.36%)	⬆️
...ving/src/main/java/ai/djl/serving/ModelServer.java	51.46% <61.90%> (+0.80%)	⬆️
...src/main/java/ai/djl/serving/wlm/ModelManager.java	79.62% <66.66%> (-10.03%)	⬇️
.../main/java/ai/djl/serving/wlm/WorkLoadManager.java	64.07% <70.00%> (ø)
.../ai/djl/serving/http/ManagementRequestHandler.java	91.05% <88.88%> (-1.19%)	⬇️
.../serving/src/main/java/ai/djl/serving/wlm/Job.java	66.66% <100.00%> (ø)
... and 1 more

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