Need better Item IDs about cmr-stac

[scottyhq]

@matthewhanson I'd like to second this. Here is a concrete example with the current "stac_version": "1.0.0-rc.4", I think it's quite common to know a Granule ID, but not an internal CMR ID, which seems to be used currently

For example, consider this Granule ID to STAC Item ID mapping:
S1A_IW_GRDH_1SDV_20170101T021007_20170101T021036_014632_017CAA_D7AD --> G1360802832-ASF

The only way I've managed to figure out that mapping is to go to Earthdata search and look at the 'information' tab:

I think for user friendliness and for the sake of interoperability it makes sense to use the producerGranuleId? That way we could access the STAC record at:

https://cmr.earthdata.nasa.gov/stac/ASF/collections/SENTINEL-1A_DP_GRD_HIGH.v1/items/S1A_IW_GRDH_1SDV_20170101T021007_20170101T021036_014632_017CAA_D7AD

instead of
https://cmr.earthdata.nasa.gov/stac/ASF/collections/SENTINEL-1A_DP_GRD_HIGH.v1/items/G1360802832-ASF