[Chore] Replace all base64 usages with faster pybase64 package (#37290)

Signed-off-by: Isotr0py <mozf@mail2.sysu.edu.cn>

tests/models/multimodal/pooling/test_colpali.py

@@ -7,9 +7,9 @@ ColPali is a multi-vector retrieval model based on PaliGemma backbone
 It produces per-token embeddings for both text and image inputs.
 """
 
-import base64
 from io import BytesIO
 
+import pybase64 as base64
 import pytest
 import torch
 from PIL import Image

tests/models/multimodal/pooling/test_colqwen3.py

@@ -7,9 +7,9 @@ ColBERT-style late interaction scoring (MaxSim). It produces per-token
 embeddings for both text and image inputs.
 """
 
-import base64
 from io import BytesIO
 
+import pybase64 as base64
 import pytest
 import torch
 from PIL import Image

tests/models/multimodal/pooling/test_llama_nemotron_vl.py

@@ -9,10 +9,10 @@ Tests for the LlamaNemotronVL model family:
 Both variants share a SigLIP vision encoder with a bidirectional LLaMA backbone.
 """
 
-import base64
 from io import BytesIO
 from pathlib import Path
 
+import pybase64 as base64
 import pytest
 import torch
 from transformers import AutoModel, AutoModelForSequenceClassification, AutoProcessor