Move gemlite layout to prototype/dtypes

[jainapurva]

This pull request moves GemlitePackedLayout and its implementation from torchao/dtypes/uintx/gemlite_layout.py to torchao/prototype/dtypes/uintx/gemlite_layout.py, and exposed it via torchao.prototype.dtypes while maintaining BC at torchao.prototype.dtypes.uintx with a deprecation warning for future torchao release.
Updates API documentation to reflect the changes

Reference Issue: #2752

[pytorch-bot]

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✅ You can merge normally! (4 Unrelated Failures)

As of commit ea40463 with merge base 9e93ab1 ():

BROKEN TRUNK - The following jobs failed but were present on the merge base:

👉 Rebase onto the `viable/strict` branch to avoid these failures

• Run Regression Tests / test (CPU 2.6, linux.4xlarge, torch==2.6.0 --index-url https://download.pytorch.org/whl/cpu, cpu) / linux-job (gh) (trunk failure)
  test/test_low_bit_optim.py::TestOptim::test_param_groups_optim_name_AdamFp8_device_cpu
• Run Regression Tests / test (CPU 2.7, linux.4xlarge, torch==2.7.0 --index-url https://download.pytorch.org/whl/cpu, cpu) / linux-job (gh) (trunk failure)
  test/test_low_bit_optim.py::TestOptim::test_param_groups_optim_name_AdamFp8_device_cpu
• Run Regression Tests / test (CPU 2.8, linux.4xlarge, torch==2.8.0 --index-url https://download.pytorch.org/whl/cpu, cpu) / linux-job (gh) (trunk failure)
  test/test_low_bit_optim.py::TestOptim::test_param_groups_optim_name_AdamFp8_device_cpu
• Run Regression Tests / test-nightly (CPU Nightly, linux.4xlarge, --pre torch --index-url https://download.pytorch.org/wh... / linux-job (gh) (trunk failure)
  test/test_low_bit_optim.py::TestOptim::test_param_groups_optim_name_AdamFp8_device_cpu

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