Fix createTempDirectory name generation

[Bodigrim]

The existing createTempDirectory uses a suboptimal schema to generate temporary directory names. Namely, it starts with foo-$processId. If there is no such folder that's it, otherwise it tries to create foo-($processId+1), then foo-($processId+2), etc.

While on the surface this is OK, in practice it puts strain on the file system. If we need to create N temporary folders, the name assignment will cycle starting from foo-$processid every time, totaling N^2 IO calls. There are also seem to be issues on Windows when one thread is removing its temporary folder, while another it trying to create the very same one.

It would be so much better if our temporary names were more diverse by construction. Yes, there might be an odd chance of a clash because someone else just accidentally created the very same folder, but we should not routinely make our own life harder.

Normally this is achieved by generating random numbers, but Cabal cannot depend on non-boot libraries such as random. So this patch uses a global counter. The approach is similar to one used by file-io for temporary files or by temporary-ospath.

(Both file-io and temporary-ospath actually have even more refined schema for name generation, getting entropy from CPU time, but I think in the interest of simplicity Cabal can get away just with a global counter)

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[ffaf1]

I tested this on my machine and it works.
As now a changelog is missing.

[Bodigrim]

As now a changelog is missing.

@ffaf1 done.