[Performance] Optimize unified checkpoint save/load speed.

[ZHUI]

PR types

PR changes

Description

For facebook/llama-7b

UC/PD Save/Load 对比	UC save	PD save
testDP8	0	0
testPP4DP2	47.13	68.36
testPP4Sharding2	25.93	41.04
testPP8	27.04	39.68
testSharding2S1DP4	93.19	145.13
testSharding2S2DP4	90.62	147.15
testSharding4S1DP2	47.6	94.75
testSharding4S2DP2	44.12	95.68
testSharding8S1	25.94	64.37
testSharding8S2	23.95	65.77
testTP2PP4	27.92	35.71
testTP2Sharding4	27.78	46.31
testTP4DP2	53.74	51.98
testTP4PP2	27.32	30.55
testTP4Sharding2	28.35	31.31
testTP8	30.63	23.75

[paddle-bot]

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[codecov]

Codecov Report

Attention: Patch coverage is 73.49398% with 66 lines in your changes are missing coverage. Please review.

Project coverage is 55.42%. Comparing base (f29a7b9) to head (32132ae).
Report is 23 commits behind head on develop.

Files	Patch %	Lines
paddlenlp/utils/safetensors.py	88.26%	23 Missing ⚠️
paddlenlp/trainer/plugins/unified_checkpoint.py	6.25%	15 Missing ⚠️
paddlenlp/transformers/model_utils.py	37.50%	15 Missing ⚠️
paddlenlp/transformers/conversion_utils.py	0.00%	12 Missing ⚠️
paddlenlp/trainer/trainer.py	0.00%	1 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #8204      +/-   ##
===========================================
+ Coverage    55.37%   55.42%   +0.04%     
===========================================
  Files          613      615       +2     
  Lines        95855    96235     +380     
===========================================
+ Hits         53083    53335     +252     
- Misses       42772    42900     +128     

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[wawltor]

LGTM