feat(flame_tiled): Allowing tilesets with images in the same folder to load

[erickzanardo]

Description

Before, when trying to use tilesets where their images were stored in the same folder as their tsx were, the loading would break.

This PR addresses that.

Checklist

• I have followed the Contributor Guide when preparing my PR.
• I have updated/added tests for ALL new/updated/fixed functionality.
• I have updated/added relevant documentation in docs and added dartdoc comments with ///.
• I have updated/added relevant examples in examples or docs.

Breaking Change?

• Yes, this PR is a breaking change.
• No, this PR is not a breaking change.

Related Issues

[spydon]

Makes sense, lgtm!

[erickzanardo]

@spydon I've updated one of the goldens. I was curious on why it changed, because in theory, what I changed, shouldn't produce different goldens. Here is a screenshoot comparing both goldens:

After debugging, I reliazed that this probably changed because since I map some paths, the order in which images are written in the atlas is different, which generates a different packing, IMO, this isn't an issue, since all the images are still there, so I just updated the golden. But let me know if you agree with that