Addresses limitations of detecting ImageFormat / ContainerFormat from the file extension

[elyoh]

Closes #799

Description

Ensures case insensitive comparison of the file extension and manually maps all supported file extensions supported by the build in container formats (BMP, JPEG, PNG, TIFF, WMP, DDS).

Additional context (optional)

Alternative approaches are possible, removing the need for hard coding any file extensions (see https://github.com/Sergio0694/ComputeSharp/issues/799#issuecomment-2142696288). Such an approach is more involved and would be a better fit if it is planned to address #800.