Drop symlink creation in tmp_path

[nicoddemus]

As discussed in #10910, seems like the symlinks created by tmp_path were useful a long time ago, during the dawn of pytest when testing pypy, and could be dropped. I personally never seen any use for it.

Should we drop them to simplify the code a bit? Any idea if we can somehow gauge if this is used?

[RonnyPfannschmidt]

We could turn it into a opt out and schedule turning it into a opt in

[bluetech]

👍 on Ronny's plan. I never used it, and it also seems unsafe in terms of running multiple pytests in parallel if you're not careful. But maybe people use it, so we should not do it immediately.

[lodagro]

For long running tests in combination with pytest-repeat i find the symlinks convenient to check on current test progress & log files. Also when post processing captured data during the test with another application than python, using the toplevel symlink there is no need to figure out what the most recent tmp_path is.