Arm backend: Replace asserts with error handling in upsample operators (#10577)

Update `op_upsample_bilinear2d.py` and `op_upsample_nearest2d.py`
classes to replace `assert` checks with `ValueError` exceptions for
improved error handling and code robustness.

- Change static shape checks from assertions to conditional raises of
  `ValueError` for clear runtime error communication.
- Replaced `assert` checks for int16 range validation of `scale_n_yx`,
  `scale_d_yx`, and `border_yx` with explicit value range checks that
  raise `ValueError` when bounds are breached.

Signed-off-by: Sebastian Larsson <sebastian.larsson@arm.com>