fix(types): explicitly set Vite hooks' this to void

[antfu]

Description

With the object hooks introduced, plugins should not rely on the implicit this from the plugin object for Vite custom plugins. This PR explicitly set them to void to provide early TypeScript hints.

Additional context

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What is the purpose of this pull request?

• Bug fix
• New Feature
• Documentation update
• Other

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[patak-dev]

I think this is needed now, so we are later able to add a context-like object as Rollup has for some of their hooks. Plugins authors may already have to review their plugins after 3.1 because of the types updates in rollup, so I think we should include it now. Let's merge it and release it in beta.1 so we give a few days to the ecosystem to test.

[aleclarson]

This breakage seems premature. Why don't we bind the plugin object to config and configResolved until we have an actual use case for a Vite-specific this context?