Problem/Motivation
#2739075: [plan] Make Place Blocks module functionality part of the Block module (etc.) wanted to move the module into block module originally, but now Layout Builder superseded it. So we should figure out a way to deprecate the module and remove it so it in Drupal 9 is not in Drupal 9.0 anymore.
Proposed resolution
1. Figure out a way to deprecate a module. We don't yet have a process.
2. Deprecate this module.
3. Remove it in Drupal 9.
Remaining tasks
Do it.
User interface changes
Module will be removed.
API changes
None.
Data model changes
None.
Release notes snippet
TBD.