fix: Explain queries should always return as an array of results

[cbaker6]

Requires a server fix parse-community/parse-server#7440. The discussion parse-community/parse-server#7442 has more information.

• Add support for an array of objects when using find by updating testcases. This falls inline with the rest of query results
• Adds support to explain a first query which was previously not available in the JS SDK

[parse-github-assistant]

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[mtrezza]

Mergeability depends on discussion parse-community/parse-server#7440 (comment).

[parse-github-assistant]

I will reformat the title to use the proper commit message syntax.

[dplewis]

@mtrezza Any news on this? I'd recommend we document either explain doesn't support first / get queries or that if explain is used an array is return here.

[mtrezza]

Whatever causes the least breaking changes while providing the most functional support.