[16.0][FIX] template_content_swapper: use _render()

[AungKoKoLin1997]

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Before this PR, when a user tried to swap the content of the survey questions page, it did not work because _render_template was called only once when the main page was opened.

This PR moves the content mapping logic from _render_template of ir.ui.view to _render of ir.qweb, which is used more consistently, ensuring content replacement works in all rendering scenarios.

@qrtl QT5304