[Relax][Frontend][TFLite] Add SCATTER_ND operator for Relax TFLite

[rknastenka]

This PR adds support for the SCATTER_ND operator in the Relax TFLite frontend.

Key Changes:

• Added handler convert_scatter_nd to parse indices and updates.
• Explicitly handles static vs dynamic shape tensor extraction via to_int_list and relax.op.tensor_to_shape.
• Uses relax.op.zeros to initialize the base array based on the updates precision dtype.
• Mapped SCATTER_ND to the corresponding relax.op.scatter_nd() target.
• Registered the translator into convert_map and provided the matching unit test in test_frontend_tflite.py.

Testing:

Passed unit tests

pytest tests/python/relax/test_frontend_tflite.py::test_scatter_nd

Related to #19412

[gemini-code-assist]

Code Review

This pull request adds support for the SCATTER_ND operator to the TFLite frontend in Relax and includes a new test case to verify its functionality. The review feedback highlights two necessary corrections: the indices tensor needs to be permuted to align with Relax's expected layout (where the index depth is the first dimension), and the shape tensor must be explicitly cast to int64 when handled dynamically to satisfy the requirements of the tensor_to_shape operator.