[PretrainedConfig] Bring back deprecation warning and fix redundant warnings

[sijunhe]

PR types

PR changes

Description

Previously, all the warnings were triggered by hasattr, which calls __get_attr__ underneath and triggered all the warning. Changing everything to access from config now.

Also remove the get from config branch of get_attr of Bart/MBart/CodeGen/Unimo/Unified Transformers

Tested that all the warnings go away after this PR

[paddle-bot]

Thanks for your contribution!

[codecov]

Codecov Report

Merging #4264 (75ae457) into develop (699a2f0) will decrease coverage by 0.04%.
The diff coverage is 97.05%.

@@             Coverage Diff             @@
##           develop    #4264      +/-   ##
===========================================
- Coverage    36.39%   36.35%   -0.05%     
===========================================
  Files          419      419              
  Lines        59058    59165     +107     
===========================================
+ Hits         21495    21509      +14     
- Misses       37563    37656      +93     

Impacted Files	Coverage Δ
paddlenlp/transformers/ernie_m/modeling.py	90.65% <ø> (ø)
paddlenlp/transformers/configuration_utils.py	67.93% <75.00%> (+0.07%)	⬆️
paddlenlp/transformers/bart/modeling.py	85.30% <100.00%> (-0.14%)	⬇️
paddlenlp/transformers/bert/configuration.py	100.00% <100.00%> (ø)
paddlenlp/transformers/bert/modeling.py	89.15% <100.00%> (+0.03%)	⬆️
paddlenlp/transformers/codegen/modeling.py	89.03% <100.00%> (-0.11%)	⬇️
paddlenlp/transformers/ernie/configuration.py	100.00% <100.00%> (ø)
paddlenlp/transformers/ernie/modeling.py	92.30% <100.00%> (+0.02%)	⬆️
...ddlenlp/transformers/ernie_layout/configuration.py	100.00% <100.00%> (ø)
paddlenlp/transformers/ernie_layout/modeling.py	76.92% <100.00%> (+0.04%)	⬆️
... and 13 more

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[wj-Mcat]

就这里一个typo 的问题，其它 lgtm。