[RSDK-9935] - Iframe only decode

[nicksanford]

Ticket

Changes:

1. Add optional i_frame_only_decode config option. false by default. If true only iframes will be decoded. Works both with lazy_decode: true and lazy_decode: false
2. Cache last returned image and the metadata of that image. Return cached response if the latest frame hasn't changed since the last camera.Image call. Bust cache when latest frame changes.
3. Warn if i_frame_only_decode config option is enabled on any codecs other than h264 and h265

Manual Tests:

- h264, i_frame_only_decode: false, lazy_decode: false, rtp_passthrough: true
- h264, i_frame_only_decode: false, lazy_decode: false, rtp_passthrough: false
- h264, i_frame_only_decode: false, lazy_decode: true, rtp_passthrough: true
- h264, i_frame_only_decode: false, lazy_decode: true, rtp_passthrough: false
- h264, i_frame_only_decode: true, lazy_decode: false, rtp_passthrough: true
- h264, i_frame_only_decode: true, lazy_decode: false, rtp_passthrough: false
- h264, i_frame_only_decode: true, lazy_decode: true, rtp_passthrough: true
- h264, i_frame_only_decode: true, lazy_decode: true, rtp_passthrough: false
- h265, i_frame_only_decode: false, lazy_decode: false
- h265, i_frame_only_decode: false, lazy_decode: true
- h265, i_frame_only_decode: true, lazy_decode: false
- h265, i_frame_only_decode: true, lazy_decode: true

[randhid]

Few nits