Use SPI manifest documentation_targets sort order for documentation archives

[daveverwer]

Discussed in #1970

^{Originally posted by Mordil August 14, 2022}
I just added SPI support for hosting DocC documentation, and the output is not following my specified ordering in the YAML file:

builder:
  configs:
    - documentation_targets: ['RediStack', 'RedisTypes', 'RediStackTestUtils']

Instead, it sorts alphabetically, which leaves the module RedisTypes as the entry point for documentation and first in the list of module documentation.

This causes me a problem, because RediStack is the main purpose of the package.

[daveverwer]

Fixed in back-end change. More details in #1976