Implicitly add COPY_DST when using create_texture_with_data

[HalfVoxel]

Connections
Fixes: #1621

Description

The documentation for device.create_texture_with_data doesn't mention that the usage must contain COPY_DST, but it also doesn't implicitly add that flag. I think it should either mention that COPY_DST is required or add it implicitly. Not sure which is the desired way to go though.

It feels kinda ugly to have to clone the descriptor. It's not a big deal performance-wise, but still.
An alternative to this would be a nicer validation error message.

[cwfitzgerald]

Hmmm. I wonder if we should just take the descriptor by value if we're just going to clone it anyway.

[HalfVoxel]

But that would be a breaking change, and it would go against the current wgpu convention, wouldn't it? I don't think there's any other place where a descriptor is passed by value?

[kocsis1david]

Wouldn't it be possible to only copy the descriptor? like let mut desc = *desc;

[cwfitzgerald]

@HalfVoxel it would be a breaking change, but we don't really mind that here. There isn't, which is what makes this a hard call. @kvark I hearby summon thee.

@kocsis1david it's not Copy.

[kvark]

Thank you!

[HalfVoxel]

I simplified the code to always do the clone. However, I left the parameter as a reference to keep the api following the wgpu conventions.

[kvark]

Thank you!