Camera: Enable flexibility for postview format

- Allow postview and capture formats to differ which could be
useful for captures requesting formats such as JPEG_R, where allowing
a lighter weight postview format can decrease its latency
- Fix how postview sizes are generated in getPostviewSupportedSizes.
Postview sizes should not be subject to the API contract mandating
support of advertised sizes for JPEG, YUV, and PRIVATE since they are
relative to the capture size

Test: Camera CTS Test for basic and advanced extensions
Bug: 317393750
Change-Id: Idd347d38493e3bfb7d7ae8a20f5103b1f7a97118