[meta][no patch] replace uses of REQUEST_TIME and time() with time service

Problem/Motivation

A time service was added to 8.3.x in #2717207: Add a time service to provide consistent interaction with time()/microtime() and superglobals.

Core code should be updated to remove deprecated uses of REQUEST_TIME and time() and others.

For more informations, see the change record.

Proposed resolution

Splitting this up into manageable chunks (#57 by @mpdonadio)

1. #3113971: Replace REQUEST_TIME in services
2. #3112298: Replace REQUEST_TIME in plugins and classes with direct container access
3. #3112295: Replace REQUEST_TIME in OO code w/o access to the container
4. #3112283: Replace REQUEST_TIME in non-OO and non-module code
5. #3112284: Replace REQUEST_TIME in tests
6. #3112290: Replace REQUEST_TIME in procedural code

Remaining tasks

1. Splitting/Creating child issues
2. Collaborating on child issues

User interface changes

API changes

Data model changes

Release notes snippet