Replace individual Apex.AI contributor emails with opensource@apex.ai

Description

Replace all individual email addresses by opensource@apex.ai.

Notes for reviewer

I think this is the preferred way. I left the names as they were except for Chris.

Pre-review checklist for the author before submitting for review

N/A

Checklist for the reviewer

Only the reviewer is allowed to make changes in this section!

Mark all the items that are done, and cross out items not applicable to this MR.

1. Basic checks
   1. The MR title describes what is being done on the ticket
   2. The MR does not require additional tests or documentation to be written
   3. The first commit has a proper commit message to be used as a basis for the squashed commit created at the very end
2. Code correctness
   1. The problem/feature is solved (reproducibly)
   2. The solution is performant enough for the use case in mind
   3. Any disabled lints inside the code or at the package level are justified
3. Open work
   1. Any added source-code comment about future work refers to a follow-up GitLab issue explicitly; e.g., // TODO #551 refactor code below

If the MR provides an improvement, don't hesitate to add a 👍 emoji for a neat line of code or a "Thanks for implementing this" comment. This will reward the MR author and prevent the review from being only about what still needs to be improved.

Post-review checklist for the author

After receiving approval:

1. All checkboxes in the MR checklist are checked or crossed out. Syntax example: 1. [ ] ~~this item crossed out~~
2. Assign MR to maintainer with sufficient rights to merge. Default: @JWhitleyWork