Add support for parent form variables

[Withalion]

fixes #4387

Add parent form to QGIS expression scopes. All parent variables should resolve correctly now.

NOTE: PR is based on #4525, wait for that merge first

[github-actions]

Coverage Report for CI Build 27632311295

Coverage increased (+0.1%) to 57.442%

Details

• Coverage increased (+0.1%) from the base build.
• Patch coverage: No coverable lines changed in this PR.
• 381 coverage regressions across 9 files.

Uncovered Changes

No uncovered changes found.

Coverage Regressions

381 previously-covered lines in 9 files lost coverage.

File	Lines Losing Coverage	Coverage
mm/app/inpututils.cpp	101	54.2%
mm/app/main.cpp	99	36.2%
mm/app/attributes/attributecontroller.cpp	89	76.2%
mm/app/synchronizationmanager.cpp	46	60.26%
mm/app/valuerelationfeaturesmodel.cpp	28	67.0%
mm/app/featuresmodel.cpp	8	38.36%
mm/app/position/providers/simulatedpositionprovider.cpp	5	85.71%
mm/app/layerfeaturesmodel.cpp	4	79.88%
mm/app/valuerelationfeaturesmodel.h	1	0.0%

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Coverage Stats

Relevant Lines:	15553
Covered Lines:	8934
Line Coverage:	57.44%
Coverage Strength:	96.15 hits per line

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💛 - Coveralls

[github-actions]

📦 Build Artifacts Ready

OS	Status	Build	Info	Workflow run
macOS Build	📬	Mergin Maps 69351 dmg	Expires: 14/09/2026	#6935
linux Build	📬	Mergin Maps 69611 x86_64	Expires: 14/09/2026	#6961
win64 Build	📬	Mergin Maps 61331 win64	Expires: 14/09/2026	#6133
Android Build	📬	Mergin Maps 824551 APK [arm64-v8a]	Expires: 14/09/2026	#8245
	📬	Mergin Maps 824551 APK [arm64-v8a]	Google Play Store	#8245
Android Build	📬	Mergin Maps 824511 APK [armeabi-v7a]	Expires: 14/09/2026	#8245
	📬	Mergin Maps 824511 APK [armeabi-v7a]	Google Play Store	#8245
iOS Build	📬		Build number: 26.06.918711	#9187