fix: prefix_file rename

[ruben-arts]

fixes: #946

Users still need to delete the .pixi/envs/default/prefix file manually after updating if it forms an issue for their solara installation

[baszalmstra]

Couldnt we not place this file in the .pixi folder instead of in the environment folder?

[ruben-arts]

Couldnt we not place this file in the .pixi folder instead of in the environment folder?

We previously discussed to keep the file close to the environment. So yeah we could but I don't remember why we decided to do it this way.

[wolfv]

@baszalmstra I think it should ideally be placed in the conda-meta folder. We seem to have a bug where rattler thinks all files in teh conda-meta folder are JSON though.

Conda does put a history and a urls.txt file there that also record some additional metadata.

[wolfv]

@ruben-arts I think you could try moving this file into conda-meta now. As long as it doesn't end with .json it should be OK.