release/2.17: v2.17: C Migrations and Bug Fixes

Bug Fixes:

* Improve slow manifest build for very large quantities of tables/segments. (Reported by Jens Wilke.)
* Fix exclusions for special files. (Reported by CluelessTechnologist, Janis Puris, Rachid Broum.)

Improvements:

* The stanza-create/update/delete commands are implemented entirely in C. (Contributed by Cynthia Shang.)
* The start/stop commands are implemented entirely in C. (Contributed by Cynthia Shang.)
* Create log directories/files with 0750/0640 mode. (Suggested by Damiano Albani.)

Documentation Bug Fixes:

* Fix yum.p.o package being installed when custom package specified. (Reported by Joe Ayers, John Harvey.)

Documentation Improvements:

* Build pgBackRest as an unprivileged user. (Suggested by Laurenz Albe.)