Resolve compiler warning for use of deprecated `KDeclarative::setupBindings`

Summary: Version 5.45 of `KDeclarative` deprecates `setupBindings` in favor of  `setupContext` and `setupEngine`, used together. Perform version check of `KDeclarative` and continue using `setupBindings` when older versions of `KDeclarative` are present. This resolves the compiler warning while allowing most users to successfully compile the application.

Test Plan:
-- Compile Spectacle normally
-- Note that compiler warning at `QuickEditor.cpp` line 77 is eliminated
-- Take a rectangular region screenshot; ensure proper operation of QML engine
-- If possible, test compiling against multiple versions of `KDeclarative` (5.45 versus minimum requirement of 5.29)

Reviewers: #spectacle, rkflx, ngraham

Reviewed By: #spectacle, rkflx

Differential Revision: https://phabricator.kde.org/D11415