1595 extend uprader to upgrade from monolithic structure to template set.xml

[quantumfate]

Adresses/Fixes #1595 .

Implements

• merge from context.xml and template.xml
• context.xml will be deleted and adapted to new template-set.xml
• updated the ContextConfigurationUpgraderTest and also added test for correct schema v6 detection
• added upgradeAndGenerate to GenerationIT in core systemtests
• activated the upgradeAndGenerate CLI test

@devonfw/cobigen

[quantumfate]

The old PR

[CLAassistant]

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