feat(coverage): support --changed option

[AriPerkkio]

Description

• Fixes Coverage with Changed #5237

I think I'll leave this part out of this PR now: #5237 (comment). That requires some discussion as it changes functionality of --changed quite much.

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[AriPerkkio]

Looks like this wasn't working as I expected it to. Files were served from Vite's cache when vite-node's fetchCache was cleared. This came up only with --changed flag as core.ts already loaded those files.

Minimal repro using vite-node:

import { createServer } from "vite";
import { ViteNodeServer } from "vite-node/server";

const server = await createServer({
  plugins: [
    {
      name: "logger",
      transform(code, id) {
        console.log(`[transform] ${id}`);
      },
    },
  ],
});
await server.pluginContainer.buildStart({});

const node = new ViteNodeServer(server);

// Should log [transform] ✅ 
console.log("transformRequest #1");
await node.transformRequest("./example.ts");


// Should log NOT [transform] ✅ 
console.log("transformRequest #2");
await node.transformRequest("./example.ts");

// Should log [transform] but it doesn't ❌ 
console.log("transformRequest #3");
node.fetchCache.clear();
node.fetchCaches.ssr.clear();
node.fetchCaches.web.clear();
await node.transformRequest("./example.ts");

node.server.close();