[Relax][TFLite] Add NON_MAX_SUPPRESSION_V5 support

[rknastenka]

Partially resolves #18928

to run the tests:

pytest tests/python/relax/test_frontend_tflite.py -v -k "nms"

[gemini-code-assist]

Code Review

This pull request implements the NON_MAX_SUPPRESSION_V5 operator in the TFLite frontend for TVM Relax, replacing a previous placeholder with a functional implementation and adding comprehensive tests. The feedback highlights that the output tensors should be truncated to max_output_size to ensure shape consistency with TFLite's behavior. Additionally, it is recommended to use the actual number of input boxes as the upper bound for index clipping to improve memory safety, and to update the IR verification tests to assert the correct output shapes based on the maximum output size.

[tlopex]

LGTM! Thanks!