[Cherry Pick] Fix distributed batch sampler

[JunnYu]

PR types

Bug fixes

PR changes

APIs

Description

num_samples 向下去整, 防止prefrech预取时候超过数据集最大长度...

# 该情况下，计算存在问题，当向上去整的时候2848会超过数据集的最大长度2844
len(self.dataset) = 2844
self.nranks = 8
int( len(self.dataset)* 1.0 / self.nranks) * self.nranks = 2840
int(ceil(len(self.dataset)* 1.0 / self.nranks)) * self.nranks = 2848

# 该情况下计算不会有问题，因为整除了
len(self.dataset) = 2844
self.nranks = 4
int( len(self.dataset)* 1.0 / self.nranks) * self.nranks = 2844
int(ceil(len(self.dataset)* 1.0 / self.nranks)) * self.nranks = 2844

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[codecov]

Codecov Report

Attention: Patch coverage is 0% with 2 lines in your changes missing coverage. Please review.

Project coverage is 55.20%. Comparing base (0f428bb) to head (1926e7b).
Report is 55 commits behind head on release/2.8.

Files with missing lines	Patch %	Lines
paddlenlp/utils/batch_sampler.py	0.00%	2 Missing ⚠️

Additional details and impacted files

@@               Coverage Diff               @@
##           release/2.8    #8691      +/-   ##
===============================================
+ Coverage        55.14%   55.20%   +0.06%     
===============================================
  Files              608      611       +3     
  Lines            94580    95055     +475     
===============================================
+ Hits             52158    52478     +320     
- Misses           42422    42577     +155     

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