build(cmake): raise minimum CMake version to 3.22

[plexoos]

Raise Simphony's declared minimum CMake version to 3.22 across the main project, standalone
examples, DD4hep plugin standalone mode, and the standalone SGLFW test target.

Ubuntu 22.04 is the intended minimum supported platform baseline for Simphony, and its system
package baseline includes CMake 3.22.1.

The project now relies on CMake features such as PROJECT_IS_TOP_LEVEL, which are supported by
CMake 3.22. Raising the declared minimum keeps the build requirements aligned with the supported
platform policy and avoids older CMake versions silently misconfiguring testing defaults.

[Copilot]

Pull request overview

Raises Simphony’s declared minimum required CMake version to 3.22 to match the Ubuntu 22.04 baseline and ensure newer CMake features (e.g., PROJECT_IS_TOP_LEVEL) behave consistently across the main build and standalone sub-projects.

Changes:

• Updated cmake_minimum_required(...) to 3.22 in the top-level build and multiple standalone/example CMake projects.
• Updated the DD4hep plugin standalone-mode CMake minimum to 3.22.
• Updated the Getting Started documentation to reflect the new CMake minimum.

Reviewed changes

Copilot reviewed 8 out of 8 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
CMakeLists.txt	Raises the project-wide minimum CMake version to 3.22.
dd4hepplugins/CMakeLists.txt	Aligns standalone DD4hep plugin build minimum CMake to 3.22.
examples/CMakeLists.txt	Updates examples’ minimum CMake to 3.22.
examples/MC_Truth/CMakeLists.txt	Updates standalone MC_Truth example minimum CMake to 3.22.
examples/async_gpu_std/CMakeLists.txt	Updates standalone async_gpu_std example minimum CMake to 3.22.
examples/async_gpu_launch/CMakeLists.txt	Updates standalone async_gpu_launch example minimum CMake to 3.22.
sysrap/SGLFW_tests/CMakeLists.txt	Updates standalone SGLFW test target minimum CMake to 3.22.
docs/getting-started.md	Documents CMake 3.22+ as the minimum prerequisite.

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