gh-130025: Correct handling of symlinks during iOS testbed framework installation.

[freakboy3742]

Corrects the handling of symlinks when the iOS testbed clones a new project:

1. Locations to source are resolved before use in the clone call.
2. Use of resolve is dropped from the evaluation of xc_framework_path and sim_framework_path. If the XCframework/framework is a symlink, we don't want to resolve the symlink to it's final location (as it may not exist)
3. If the XCframework on sim framework doesn't exist at all, the unlink is now a no-op.
4. If no framework is specified, but the existing framework is a relative symlink, it is re-written relative to the new framework location (and similarly for the simulator framework).

• Issue: iOS testbed clone breaks on some symlinks #130025

[freakboy3742]

This needs to be tested on the iOS buildbot, but the buildbot is currently offline for maintenance.

[freakboy3742]

!buildbot iOS

[bedevere-bot]

🤖 New build scheduled with the buildbot fleet by @freakboy3742 for commit 5ffdbf6 🤖

The command will test the builders whose names match following regular expression: iOS

The builders matched are:

• iOS ARM64 Simulator PR

[freakboy3742]

Buildbot is back online (for now at least... there will likely be some more maintenance in the near future) - but I can at least confirm the testbed still works in CI with this change.

[ned-deily]

LGTM (without actually testing)

[miss-islington-app]

Thanks @freakboy3742 for the PR 🌮🎉.. I'm working now to backport this PR to: 3.13.
🐍🍒⛏🤖

[bedevere-app]

GH-130073 is a backport of this pull request to the 3.13 branch.

[hugovk]

@python/organization-owners Please block @mfxrhxn for abuse (see also #128450 (review)).

I also reported them to GitHub.