Remove intermediate temporary file for CMD activation

[kenodegard]

Description

Previously conda activate in Windows CMD would first create a temporary file at %TMP%\conda-%RANDOM%\conda.tmp, it would then call conda shell.cmd.exe activate which in turn would write the activation code to another temporary file (with a randomized name), this randomized temporary file name is then printed to stdout and stored in the first temporary file.

This PR removes the second temporary file and instead redirects the activation code to the first temporary file.

Xref #13610

Checklist - did you ...

• [ ] Add a file to the news directory (using the template) for the next release's release notes?
• [ ] Add / update necessary tests?
• [ ] Add / update outdated documentation?