Add support for On-The-Fly Dynamic SafeTensors loading. #13988

Job	Run time
Analyze Code Changes for Test Orchestration	19s
build_and_upload_maxtext_package / build_and_upload	32s
maxtext_tpu_pathways_unit_tests / run	21m 5s
maxtext_tpu_pathways_integration_tests / run	8m 12s
All Notebooks Passed	3s
cpu-unit tests / cpu-unit / run	6m 58s
tpu-unit tests / tpu-unit / run	24m 57s
cpu-post-training-unit tests / cpu-post-training-unit / run	5m 41s
cpu-unit tests / cpu-unit / run	3m 7s
tpu-post-training-unit tests / tpu-post-training-unit / run	5m 44s
tpu-integration tests / tpu-integration / run	24m 57s
cpu-unit tests / cpu-unit / run	4m 8s
gpu-integration tests / gpu-integration / run	8m 20s
cpu-unit tests / cpu-unit / run	9m 45s
gpu-unit tests / gpu-unit / run	5m 7s
maxtext_jupyter_notebooks	-1s
Notify failed build	3s
All Required Tests Passed	3s
Investigate failed build	0s
	2h 9m 0s

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