Accelerate the fetch and test install by run only for newly added plugin

[unkcpz]

When new plugin is added to the plugins.yaml, the preview CI will go through all plugins to test, which is time-consuming and hides the test output information among other plugins output.
The make_pages can accept packages and only fetch and test install on those plugins. If we can ensure the new plugin is always added at the end of plugins.yaml then we can get the plugin name and in CI only run the test for it.