MAINTENANCE. Cleaning up stale PRs.

Closing the following PRs due to requests or unresponsive users.

Closes #13923
Closes #14462
Closes #13123
Closes #14423 (requested by srowen)
Closes #14424 (requested by srowen)
Closes #14101 (requested by jkbradley)
Closes #10676 (requested by srowen)
Closes #10943 (requested by yhuai)
Closes #9936
Closes #10701
Closes #10474
Closes #13248
Closes #14347
Closes #10356
Closes #9866
Closes #14310 (requested by srowen)
Closes #14390 (requested by srowen)
Closes #14343 (requested by srowen)
Closes #14402 (requested by srowen)
Closes #14437 (requested by srowen)
Closes #12000 (already merged)

Author: Marcelo Vanzin