Fix mixed precision in TF models
# What does this PR do?

This PR aims to fix the mixed precision issues when `tf.keras.mixed_precision.experimental.set_policy()` is set to something else than `tf.float32`.  In the same page, this PR aims to fix some TFLite quantization issues.

Before to further continue this PR, the PR #9418 has to be merged.

Fixes # (issue)

#7052 
