Add 3.7.16, 3.8.16, 3.9.16

[chadac]

Make sure you have checked all steps below.

Prerequisite

• Please consider implementing the feature as a hook script or plugin as a first step.
  • pyenv has some powerful support for plugins and hook scripts. Please refer to Authoring plugins for details and try to implement it as a plugin if possible.
• Please consider contributing the patch upstream to rbenv, since we have borrowed most of the code from that project.
  • We occasionally import the changes from rbenv. In general, you can expect changes made in rbenv will be imported to pyenv too, eventually.
  • Generally speaking, we prefer not to make changes in the core in order to keep compatibility with rbenv.
• My PR addresses the following pyenv issue (if any)

Description

• Add Python versions 3.7.16, 3.8.16, 3.9.16 per CONTRIBUTING guidelines
• Port pre-existing patches from 3.7.15
• Hashes generated using curl <url> | sha256sum

Tests

• All versions install from the Docker image.