Camera: Prune depth samples with low confidence

Depth samples with low confidence can skew the
near/far values and impact the range inverse coding.
Avoid using such samples when searching for the near
and far points and clamp their values if necessary.

Bug: 132248813
Test: Camera CTS
Change-Id: I7dc134b50e46c664f9fc8750b9b9b37c416c9afe