CUMULUS-2688: Granule doc updates

[npauzenga]

This updates the Granule docs to reflect changes in https://bugs.earthdata.nasa.gov/browse/CUMULUS-2688. The key updates here are modifying all impacted Granule endpoints to fetch granules by both granuleId and collectionId, not just granuleId as before.

These doc updates correspond to the changes made in these PRs:

nasa/cumulus#2978
nasa/cumulus#3000
nasa/cumulus#3022

Notes:

• This PR targets a new rds-phase-3 branch that should be merged when phase 3 is released.
• The old method of fetching granules by granuleId alone is still technically available in the API, though deprecated. Users could use e.g. GET /granules/:granuleId. I removed references to this behavior from the docs because we don't want to encourage these lookups after phase 3.

[npauzenga]

@jennyhliu what would you think about merging this to the rds-phase-3 branch? We have more work to do on the core side to validate that we support multiple granules with the same granuleId but that would all need to be done before phase-3 and these docs are released I think.

[jennyhliu]

Make sure we have the tickets (https://bugs.earthdata.nasa.gov/issues/?jql=labels%20%3D%20RDS_Phase_3) done before merging the rds-phase-3 to master.

[npauzenga]

Added a note to the "Release Phase 3" ticket to also merge the feature branch in the cumulus-api repo: https://bugs.earthdata.nasa.gov/browse/CUMULUS-2987