Avoid using /tmp

[johnhany97]

Attempts to fix #2418

I realised that we already attempt to rename, and if that failed, we attempt to copy then delete the file. However, this seems to still cause Invalid cross-device link error.

My proposal is to just avoid storing the temporary file in /tmp, and instead use the same cache dir we already use for writing the .json files.

[johnhany97]

Given the nondeterministic nature of the issue at hand, i'm likely to try and get a patched version of mamba with this change and run it for a bit on our internal development infra to see if the issue still pops up or not. I won't be able to do so for at least a week though.

[jonashaag]

Not sure if this fixes anything, see discussion here: #2239 (comment)

[johnhany97]

I guess the alternative then would be to read the file and write it again ourselves to the new location? Happy to repurpose the code to do so.

[wolfv]

I think that's a good idea, to create the file next to the final destination. Conda is doing it like this as well, and it will definitely get rid of this issue!