Semantic snippets: Work on ctor snippet after modifiers

[DoctorKrolic]

Originally I wanted to make ctor snippet appear after accessibility modifiers and static keyword, so user can type e.g. private ctor and immediately get private constructor instead of either typing it all himself or changing accessibility modifier after activating ctor snippet. Part of that work required to move GenerateSnippetTextChangeAsync to CSharpConstructorSnippetProvider since PrecedingModifiers are only available on C# level. I refactored the method to use more C#-specific APIs to get other things, e.g. used CSharpSyntaxContext.ContainingTypeDeclaration instead of searching for node ourselves. As it turned out, these APIs are smarter and handle some edge cases, that were not handled before. So this PR also:
Fixes #68176
Fixes AB#1818584
Closes #68177 (as a replacement)

[DoctorKrolic]

@sharwell What are we gonna do with this PR?

[sharwell]

@DoctorKrolic My PR to fix this is going to be in #71872. I was delayed by the unexpected failure in the integration test pipeline but should be able to move it forward over the next few hours.

[DoctorKrolic]

My PR to fix this is going to be in #71872

I'll wait for it to merge first and then fix this one considering its changes. I'll appreciate if you prioritize it a bit to unblock me though

[akhera99]

Looks good, thanks for the contribution @DoctorKrolic!