Add integration test for truncated-normal op

[AzizZayed]

Description

Add the integration test for the truncated-normal operation. This test verifies the sample mean is within a certain range from the theoretical mean. It also checks the truncation, testing if all the sample points are within 2 standard deviations from the mean.

[codecov-commenter]

Codecov Report

Merging #1036 (1011ad0) into master (4119d0d) will increase coverage by 0.08%.
The diff coverage is n/a.

@@             Coverage Diff              @@
##             master    #1036      +/-   ##
============================================
+ Coverage     69.97%   70.06%   +0.08%     
- Complexity     5110     5117       +7     
============================================
  Files           504      504              
  Lines         22629    22629              
  Branches       2375     2375              
============================================
+ Hits          15835    15855      +20     
+ Misses         5523     5501      -22     
- Partials       1271     1273       +2     

Impacted Files	Coverage Δ
api/src/main/java/ai/djl/ndarray/NDManager.java	57.43% <0.00%> (+0.67%)	⬆️
...pi/src/main/java/ai/djl/ndarray/BaseNDManager.java	57.40% <0.00%> (+7.40%)	⬆️
...ain/java/ai/djl/tensorflow/engine/TfNDManager.java	89.68% <0.00%> (+7.93%)	⬆️
api/src/main/java/ai/djl/util/RandomUtils.java	87.50% <0.00%> (+12.50%)	⬆️

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