[WIP] Fix uneccessary confirmation dialog when reopenning a form

[ValentinBuira]

Previously we kept the left most form component in the stackview for performance but it prevent the call to recalculateDerivedItems and the appropriate HasAnyChanges signal

This PR solve the issue by destroying the last form component and rebuild it each time a form is open

May partially solves #3671

[github-actions]

Pull Request Test Coverage Report for Build 12138645669

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 178 unchanged lines in 4 files lost coverage.
• Overall coverage increased (+0.05%) to 60.408%

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Files with Coverage Reduction	New Missed Lines	%
input/core/merginapi.h	1	97.56%
input/core/merginprojectmetadata.cpp	4	89.25%
input/app/mmstyle.h	49	1.95%
input/core/merginapi.cpp	124	78.72%

Totals
Change from base Build 12135499446:	0.05%
Covered Lines:	7876
Relevant Lines:	13038

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💛 - Coveralls

[tomasMizera]

With this fix in place, we should be safe to revert the fix introduced in #2880, @alexd0793 When you test this, please test also this issue: #2879

@ValentinBuira let's also bear in mind that activeFormIndex will now often (when no form is opened) be -1 (previously 0). I checked the code and even though it works a bit differently now, I do not see any issue with it.

[tomasMizera]

Suggested change

	else{
	else {