[AMDGPU] Support double type in atomic optimizer. (#84307)

Presently the atomic optimizer supports only 32-bit operations. Plan is
to extend the atomic optimizer for 64-bit operations for compute and
graphics. This patch extends support for double type for `uniform
values` only. Going forward, will extend the support for divergent
values. Adding support for divergent values requires
extending/legalizing readfirstlane, readlane, writelane, etc ops for
64-bit operations to avoid `bitcast` noise that we have currently.

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Authored-by: Pravin Jagtap <Pravin.Jagtap@amd.com>