Ftw.testing

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- Implement console script testing layer.
[jone]

- Implement TEMP_DIRECTORY testing layer.
[jone]

- Implement COMPONENT_REGISTRY_ISOLATION layer.
[jone]

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- Add patcher for disabling quickinstaller snappshotting in tests.
[jone]

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- Generic Setup uninstall test: Add a second test that uses Portal Setup for
uninstallation. This makes sure that Portal Setup uninstallation behaves the same as
quickinstaller uninstallation.
[deif]

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- Generic Setup uninstall test: Remove is_product option, since we
require an uninstall external method which requires the package
to be a product anyway.
[jone]

- Generic Setup uninstall test: test that there is an uninstall external method.
Uninstall external methods are still necessary today for properly uninstalling
a package.
[jone]

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- Generic Setup test: use quickinstaller for uninstalling.
[jone]

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- Also install profile dependencies before creating a snapshot.
[deif]