Translating en/internal folder docs to Japanese 🇯🇵 (#26747)

* Add translation to fitst 3 file of internal folder

* Update Toctree.md and add files

* Update docs/source/ja/internal/generation_utils

Co-authored-by: Steven Liu <59462357+stevhliu@users.noreply.github.com>

* Rename generation_utils file

* rename pipelines_utils.md

* Change file names

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Co-authored-by: Steven Liu <59462357+stevhliu@users.noreply.github.com>

docs/source/ja/internal/modeling_utils.md

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+<!--Copyright 2020 The HuggingFace Team. All rights reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with
+the License. You may obtain a copy of the License at
+
+http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on
+an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the
+specific language governing permissions and limitations under the License.
+
+⚠️ Note that this file is in Markdown but contain specific syntax for our doc-builder (similar to MDX) that may not be
+rendered properly in your Markdown viewer.
+
+-->
+
+# カスタムレイヤーとユーティリティ
+
+このページには、ライブラリで使用されるすべてのカスタム レイヤーと、モデリングに提供されるユーティリティ関数がリストされます。
+
+これらのほとんどは、ライブラリ内のモデルのコードを研究する場合にのみ役に立ちます。
+
+
+## Pytorch custom modules
+
+[[autodoc]] pytorch_utils.Conv1D
+
+[[autodoc]] modeling_utils.PoolerStartLogits
+    - forward
+
+[[autodoc]] modeling_utils.PoolerEndLogits
+    - forward
+
+[[autodoc]] modeling_utils.PoolerAnswerClass
+    - forward
+
+[[autodoc]] modeling_utils.SquadHeadOutput
+
+[[autodoc]] modeling_utils.SQuADHead
+    - forward
+
+[[autodoc]] modeling_utils.SequenceSummary
+    - forward
+
+## PyTorch Helper Functions
+
+[[autodoc]] pytorch_utils.apply_chunking_to_forward
+
+[[autodoc]] pytorch_utils.find_pruneable_heads_and_indices
+
+[[autodoc]] pytorch_utils.prune_layer
+
+[[autodoc]] pytorch_utils.prune_conv1d_layer
+
+[[autodoc]] pytorch_utils.prune_linear_layer
+
+## TensorFlow custom layers
+
+[[autodoc]] modeling_tf_utils.TFConv1D
+
+[[autodoc]] modeling_tf_utils.TFSequenceSummary
+
+## TensorFlow loss functions
+
+[[autodoc]] modeling_tf_utils.TFCausalLanguageModelingLoss
+
+[[autodoc]] modeling_tf_utils.TFMaskedLanguageModelingLoss
+
+[[autodoc]] modeling_tf_utils.TFMultipleChoiceLoss
+
+[[autodoc]] modeling_tf_utils.TFQuestionAnsweringLoss
+
+[[autodoc]] modeling_tf_utils.TFSequenceClassificationLoss
+
+[[autodoc]] modeling_tf_utils.TFTokenClassificationLoss
+
+## TensorFlow Helper Functions
+
+[[autodoc]] modeling_tf_utils.get_initializer
+
+[[autodoc]] modeling_tf_utils.keras_serializable
+
+[[autodoc]] modeling_tf_utils.shape_list