feat: add defineUtility, update utilities and clean plugins

[florian-lefebvre]

In this PR:

• New defineUtility utility
• All utilities are reworked to use it
• All plugins except hasVitePluginPlugin have been removed as they do not bring anything compared to utilities
• Docs have been revamped
• Plugins have been de-emphasized from docs as they will be reworked in 0.9
• Playground and tests have been updated

Unfortunately, the PR got way too big so here is how you can review it without losing your sanity:

• On the files tab only review changes made outside of docs
• Review docs carefully by visiting the preview

• I need confirmation on the hasVitePluginPlugin implementation. Does the updateConfig patching still work now that we pass params directly?

TODO:

• [x] Add defineUtility
• [x] Update utilities
• [x] Clean plugins
• [x] Update playground
• [x] Update tests
• [x] Update docs
  • [x] New utility
  • [x] Utilities
  • [x] Breaking changes (oh boy)
  • [x] Recommend template
  • [x] Check all docs
• [x] Changeset
• [x] Check hasVitePlugin
• [x] Test!!
• [x] PR description
• [x] How to review

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[BryceRussell]

I am currently testing hasVitePluginPlugin in the playground, and it looks like it is not working, but I am still investigating

[BryceRussell]

The overriding issue can be fixed inside defineIntegration.ts by spreading the params after the plugins instead of before:

  return providedHooks[hookName]?.({
-   ...params,
    ...Object.fromEntries(
        plugins.map((plugin) => [
            plugin.name,
            plugin.implementation(params, { name }),
        ]),
    ),
+   ...params,
  } as any);