1. Avoid losing plugin if plugin failed to load when replaying
When in replay process, the plugin should always be added to the plugin manager,
even if that plugin failed to be loaded.
2. `show plugin` statement should show all plugins, not only the successfully installed plugins.
3. plugin's name should be unique globally and case insensitive.
4. Avoid creating new instances of plugins when doing metadata checkpoint.
5. Add a __builtin_ prefix for builtin plugins.
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