Refactor Studio GRIDV regression test module

[rhamenator]

Closes #5230

Structural-only #2564 slice.

• Moves the contiguous stable-selection GRIDV report/label regression family to a focused included test module.
• Keeps the same aggregate executables, declarations, invocation order, fixtures, Studio host JSON, report/label, localization, and machine contracts.
• Confirms the moved body is byte-identical to the v1-development source apart from removal of its terminal blank line required by the repository whitespace gate.

Validation:

• TMPDIR=/home/rich/temp CMake Debug build of test_studio_host_report_direct_setting_fields and test_studio_host_report_page_setup_fields.
• CTest exact pair passed 2/2.