[impeller] Refactored backend specific feature checks to capabilities

[iskakaushik]

part of flutter/flutter#120498

[flutter-dashboard]

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[chinmaygarde]

Minor nit about the setter names, but otherwise LGTM.

[iskakaushik]

renaming to IDeviceCapabilities short for ImpellerDeviceCapabilities to avoid windows conflicts:

ninja -t msvc -e environment.x64 -- C:\b\s\w\ir\cache\goma\client/gomacc.exe ../../buildtools/windows-x64/clang/bin/clang-cl.exe  /nologo /showIncludes @obj/flutter/impeller/renderer/backend/gles/gles.surface_gles.obj.rsp /c ../../flutter/impeller/renderer/backend/gles/surface_gles.cc /Foobj/flutter/impeller/renderer/backend/gles/gles.surface_gles.obj /Fdobj/flutter/impeller/renderer/backend/gles/gles_cc.pdb
In file included from ../../flutter/impeller/renderer/backend/gles/surface_gles.cc:9:
../../flutter\impeller/renderer/backend/gles/context_gles.h(44,19): error: template argument for template type parameter must be a type
  std::unique_ptr<DeviceCapabilities> device_capabilities_;
                  ^~~~~~~~~~~~~~~~~~
C:\b\s\w\ir\kitchen-checkout\depot_tools\win_toolchain\vs_files\1023ce2e82\Windows Kits\10\Include\10.0.20348.0\um\wingdi.h(3946,29): note: expanded from macro 'DeviceCapabilities'
#define DeviceCapabilities  DeviceCapabilitiesW
                            ^~~~~~~~~~~~~~~~~~~
C:\b\s\w\ir\kitchen-checkout\depot_tools\win_toolchain\vs_files\1023ce2e82\VC\Tools\MSVC\14.29.30133\include\memory(3273,20): note: template parameter is declared here
    template <class, class>
                   ^
In file included from ../../flutter/impeller/renderer/backend/gles/surface_gles.cc:9:
../../flutter\impeller/renderer/backend/gles/context_gles.h(73,9): error: unknown type name 'DeviceCapabilitiesW'; did you mean 'DeviceCapabilities'?
  const DeviceCapabilities& GetDeviceCapabilities() const override;
        ^~~~~~~~~~~~~~~~~~
        DeviceCapabilities
C:\b\s\w\ir\kitchen-checkout\depot_tools\win_toolchain\vs_files\1023ce2e82\Windows Kits\10\Include\10.0.20348.0\um\wingdi.h(3946,29): note: expanded from macro 'DeviceCapabilities'
#define DeviceCapabilities  DeviceCapabilitiesW
                            ^
../../flutter\impeller/renderer/device_capabilities.h(13,7): note: 'DeviceCapabilities' declared here
class DeviceCapabilities {
      ^

We can rename later if needed.