[3.x] Sanitize input to ImageTexture::set_data() to prevent bad memory access

[nobuyukinyuu]

Fixes #54930. As part of the refactoring of texture.cpp, the equivalent checks should already be in the corresponding method in master.

[nobuyukinyuu]

Flags have changed to separate fields in 4.0; the state of the mipmaps field seems to be different to flags & FLAG_MIPMAPS at the time get_data() is called by the engine in many cases which I'm not clear on. To check mipmaps I pulled from get_data() but the sanitizer build doesn't like this because of the potential null pointer access. I can add a check for image_stored before doing a mipmap check, but I don't know if having the branch statement in this method is undesirable. In any case, I'll try and see if this satisfies the sanitizer build check.

[Macksaur]

Does this change work with VisualServer.texture_set_shrink_all_x2_on_set_data? and also with GLES2 having to resize_to_po2 to support older hardware?

[nobuyukinyuu]

@Macksaur After testing, I notice that setting VisualServer.texture_set_shrink_all_x2_on_set_data(true) will cause image data of the original to report the original dimensions, but duplicating the original will pull from the shrunk texture once bound to the texture. Chaining duplicates from the bound texture will do the same thing and half the resolution. Considering the nature of the set_data() method, it's probably sill up to you to maintain awareness of the state of the VisualServer texture shrink setting when writing your bind method. After performing resize() and create_from_image() with the shrink setting enabled, the actual raw image size and what set_data() expects will no longer match. This PR should, however, still catch the discrepancy and prevent OOB memory access if you were to naively attempt , like so:

I don't know if this discrepancy would be considered another bug, but I feel like it is outside the scope of this PR, as it's not an issue introduced by these changes. It may require a separate bug report, testing on the 4.0 branch, etc. Hope that helps.