Log Message:
pkgin: Update to 23.8.0.

## Version 23.8.0 (2023-08-16)

This is the biggest overhaul of pkgin yet!  As well as fixing many bugs, pkgin
23.8.0 runs "pkgin -n upgrade" over 2,000x faster on a test system \ 
with 12,663
packages installed compared to 22.10.0 (1.4 seconds vs over 54 minutes).

 * Large overhaul of dependency resolution code, fixing many upgrade issues,
   providing significant performance improvements, and improving code and
   logic readability.

 * Add support for SUPERSEDES.

 * Fix install and removal ordering.

 * Improve and fix handling of "keep" packages, using "pkg_add \ 
-A" to
   correctly install automatic packages rather than applying keep or unkeep
   flags afterwards.

 * Output improvements, sorting packages alphabetically and providing a
   simple progress counter.  Fix unwanted output that could end up mixed
   with package paths in "pkgin export".

 * Correct handling of +REQUIRED_BY for reverse dependencies, fixing
   DEPENDS that use alternate matches.

 * Many internal code improvements, memory leaks plugged, and compiler
   warnings eradicated.

Fixes at least the following issues:

 * NetBSDfr/pkgin#10
 * NetBSDfr/pkgin#44
 * NetBSDfr/pkgin#79
 * NetBSDfr/pkgin#95
 * NetBSDfr/pkgin#97
 * NetBSDfr/pkgin#110
 * NetBSDfr/pkgin#113
 * NetBSDfr/pkgin#128
 * NetBSD PR#51465
 * NetBSD PR#56683