Allow dynamic code within defineRouteMeta

[pi0]

Related:

• Dynamically computed meta with defineRouteMeta() #2641
• Use generator with nitro openapi #2912

Experimental route meta (#2102) (docs) only allows static definition like this:

defineRouteMeta({
  openAPI: {
    tags: ["test"],
    description: "Test route description",
    parameters: [{ in: "query", name: "test", required: true }],
  },
});

However, users might want to generate it with other tools like zod.

In order to support this, we need to update handlers-meta rollup plugin to detect defineRouteMeta and actually evaluate (run) the code necessary in place since by-design this information should be statically extracted into the bundle.