Support GEDI subsetting across collections

[chuckwondo]

Laura Duncanson mentioned in Slack that being able to subset across GEDI collections would be very useful: esa-nasa-maap.slack.com/archives/C01308ZHELF/p1665152994817519

Currently, the subsetting algorithm allows subsetting only a single GEDI collection (as specified by user input, such as "L4A"). Therefore, in order for users to subset and combine across multiple GEDI collections, they must run a separate job for each collection they wish to subset (using identical input values, other than the DOI for the collection), and must then manually concatenate the results of each job.

Implementing this enhancement would do all of that manual effort on behalf of the user, thus allowing the user to simply provide a list of DOIs (rather than only a single DOI) to kick off a single job that results in the combined output.

A comment from @wildintellect:

That's an interesting use case. I see an issue if any quality filtering is done the same results might not be returned. I think the key is to have users make sure to include Shot Number in their results, then we could provide another algorithm or script example that does a table merge based on Shot Number.

Given Alex's input, rather than modifying the subsetting code to handle multiple collections within a single job, the acceptance criterion for this is to provide example code (perhaps in a notebook) for:

• kicking off multiple subsetting jobs (1 per GEDI collection of interest)
• awaiting all jobs to complete
• joining results