Prepare 2.44 development

[cdietrich]

• bump version
• bootstrap against new release
• 2.43 final ref project
• 2.44 ref projects
• r202606 target
• api diff
• xtext/maven-xtext-example (bump to new release)
• releases/2026-09 in latest target and wizard/reference projects
• 2026-09 orbit in targets + wizard/reference projects
• next i-builds in latest
• oomph