[3006.x] Keep extras directory when upgrading Salt on macOS

[twangboy]

What does this PR do?

Fixes an issue with the macOS installer so that the extras-3.10 directory isn't removed during an upgrade.

What issues does this PR fix or reference?

Fixes: #65073

Merge requirements satisfied?

[NOTICE] Bug fixes or features added to Salt require tests.

• Docs
• Changelog - https://docs.saltproject.io/en/master/topics/development/changelog.html
• Tests written/updated

Commits signed with GPG?

Yes

[s0undt3ch]

Can we also have a pkg test which confirms that a previously existing package installed in extras-3.x is kept during upgrades?

And if we have a test like that(we do for linux?) let's make sure it also runs on macos.

[MKLeb]

Can we also have a pkg test which confirms that a previously existing package installed in extras-3.x is kept during upgrades?

And if we have a test like that(we do for linux?) let's make sure it also runs on macos.

There is a test for this in test_salt_upgrade, but right now it's not accurately testing it. There is a fix so that it actually tests it properly in my downgrade tests PR here. If we think it's a good idea, I can port these changes and the similar changes made for windows over to that downgrade tests PR and verify that it's working properly.