d3d11: Add "sampler-filter" propoerty for user to be able to select filter method

Add "sampler-filter" property to d3d11videosink,
d3d11convert, d3d11colorconvert, d3d11scale, and d3d11compositor
elements. It's similar to "method" property of videoscale.

This sampler-filter will be mapped to D3D11_FILTER value
which is used for filter method of sampler state.

Currently supported methods are
- Point (least expensive, worst visual quality)
- Bilinear
- Trilinear (default)
- Anisotropic (most expensive, best visual quality)

See also https://docs.microsoft.com/en-us/visualstudio/debugger/graphics/point-bilinear-trilinear-and-anisotropic-texture-filtering-variants?view=vs-2019
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