Changes

Configure Plug-in Start Levels to enable slf4j-2 logging

For all products this means that the implementation of the OSGi Service
Loader Mediator Specification supplied by Eclipse-Platform, namly the
'org.apache.aries.spifly.dynamic.bundle' bundle has to be auto-started
at level two, like it is already done for the Eclipse SDK managed by
Eclipse-Platform.

All products that contain the slf4j.simple logging back-end, need to
auto-start slf4j.simple as well.
Additionally a VM-property is set to turn slf4j.simple off by default.
A user can then configure it as desired by modifying/setting the
corresponding system-properties in the eclipse.ini, as defined in the
SimpleLogger doc:
https://www.slf4j.org/api/org/slf4j/simple/SimpleLogger.html

If a product uses the o.e.m2e.logback feature, and therefore logback as
logging back-end, nothing needs to be done. The m2e.logback
feature already performs all necessary configuration upon its
installation.

Fixes https://github.com/eclipse-packaging/packages/issues/27

Don't add slf4j.simple to products that don't include slf4j already

This is a follow up to #27 to workaround the committers, php and scout
products not including slf4j, so therefore not being able to have
start levels for them.

The org.apache.aries.spifly.dynamic.bundle start level for these bundles is
kept to allow installing, for example m2e logback.

Prepare repo for 2023-09 M3

Set version qualifiers with setGitDate script