[DT][NFC] Refactor encoding utilities. (2/n) #15314

Job	Run time
setup / setup	17s
Build Packages / Linux Release (x86_64)	12m 6s
Unit Test / Linux (x86_64)	2m 47s
Regression Test / test_models :: cpu_llvm_task	1m 44s
Regression Test / test_regression_suite :: cpu_llvm_task	10m 33s
Regression Test / test_models :: amdgpu_rocm_mi250_gfx90a	7m 35s
Test AMD MI250 / test_mi250	6m 10s
Regression Test / test_regression_suite :: amdgpu_rocm_mi250_gfx90a	9m 32s
Regression Test / test_models :: amdgpu_rocm_mi300_gfx942	2m 48s
Test AMD MI300 / test_mi300	1m 54s
Regression Test / test_regression_suite :: amdgpu_rocm_mi300_gfx942	6m 10s
Regression Test / test_models :: amdgpu_vulkan	1m 41s
Test AMD W7900 / test_w7900	1m 49s
Test ONNX / test_onnx_models :: cpu_llvm_task	2m 54s
Test Android / android_arm64	6m 48s
Test ONNX / test_onnx_ops :: cpu_llvm_sync	4m 15s
Test PJRT plugin / Build and test (ubuntu-20.04, cpu)	3m 55s
Test ONNX / test_onnx_ops :: amdgpu_rocm_rdna3	8m 59s
Test RISC-V 64 / riscv64	5m 45s
Test TensorFlow / Linux (x86_64)	1m 28s
Test ONNX / test_onnx_ops :: amdgpu_vulkan	1m 45s
	1h 40m 55s

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