Move DeviceFlags and CheckAlphaTypeAndGetFlags to skgpu::BaseDevice

skgpu::v2::Device will also need both of these so move them somewhere accessible

Bug: skia:11837
Change-Id: Iacaf0332da933515451056eeda62949b049378b7
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/446180
Reviewed-by: Michael Ludwig <michaelludwig@google.com>
Commit-Queue: Robert Phillips <robertphillips@google.com>
11 files changed