a longstanding issue in zink has been the scenario where a dmabuf is
created for e.g., RGBA8888, then the app tries to do SRGB, but the driver
doesn't support mutable formats with the dmabuf modifier. in this scenario, the app
would either crash or break unpredictably
by reusing the existing transient mechanism (previously only for msrtss emulation),
these dmabufs can instead have a shadow image which handles mutable formats and
then syncs back to the main image when necessary
this should greatly improve the situation on e.g., Intel
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/39336>
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