Promote project.rootDirectory for interpolation and profile activation

[slawekjaranowski]

• Added support for ${project.rootDirectory} to reference the project's root directory (containing the .mvn directory).
• Enhanced profile activation to support exists and missing checks based on ${project.rootDirectory}.

fix #11909

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[slawekjaranowski]

IT:

• Promote project.rootDirectory maven-integration-testing#422