Save a denoised frame when clicking "Save current frame"

[leMaik]

Currently, the denoiser only denoises the image after it has been rendered to the full configured SPP.

Originally raised by @NJDaeger:

I was wondering if that button could be changed to either save the denoised image by default or to give the option to save the denoised image vs the non denoised image either that or another button be added into the denoiser tab to save the denoised version of the current frame which would probably make more sense