feat(ts): expose MiddlewareConfig interface (#61576)

### What?

Expose the `MiddlewareConfig` interface.

### Why?

You can now `import type { MiddlewareConfig } from "next/server"` to
type the `config` object in your `middleware.ts` file.

Now you an type the entire file for example like so:
```ts
// middleware.ts
import type { NextMiddleware, MiddlewareConfig } from "next/server"

export const middleware: NextMiddleware = async (req) => {
  //...
}

export const config: MiddlewareConfig = {
  //...
}
```

### How?

Re-exported the interface from its current location via
`server/web/types`, to colocate it with `NextMidldeware`.

I wonder if we could somehow type this file automatically, but it might
be dependent on microsoft/TypeScript#38511

Closes NEXT-2308

[Slack
thread](https://vercel.slack.com/archives/C03S9JCH2Q5/p1706287433026409?thread_ts=1706058855.423019&cid=C03S9JCH2Q5),
[Slack
thread](https://vercel.slack.com/archives/C03KAR5DCKC/p1706659724141899)

packages/next/server.d.ts

@@ -7,7 +7,7 @@ declare global {
 export { NextFetchEvent } from 'next/dist/server/web/spec-extension/fetch-event'
 export { NextRequest } from 'next/dist/server/web/spec-extension/request'
 export { NextResponse } from 'next/dist/server/web/spec-extension/response'
-export { NextMiddleware } from 'next/dist/server/web/types'
+export { NextMiddleware, MiddlewareConfig } from 'next/dist/server/web/types'
 export { userAgentFromString } from 'next/dist/server/web/spec-extension/user-agent'
 export { userAgent } from 'next/dist/server/web/spec-extension/user-agent'
 export { URLPattern } from 'next/dist/compiled/@edge-runtime/primitives/url'

packages/next/src/build/analysis/get-page-static-info.ts

@@ -24,7 +24,12 @@ import { PAGE_TYPES } from '../../lib/page-types'
 // Don't forget to update the next-types-plugin file as well
 const AUTHORIZED_EXTRA_ROUTER_PROPS = ['maxDuration']
 
+/** @see https://nextjs.org/docs/app/api-reference/file-conventions/middleware#config-object-optional */
 export interface MiddlewareConfig {
+  /**
+   * @see https://nextjs.org/docs/app/api-reference/file-conventions/middleware#matcher
+   * @see https://nextjs.org/docs/app/building-your-application/routing/middleware#matching-paths
+   */
   matchers?: MiddlewareMatcher[]
   unstable_allowDynamicGlobs?: string[]
   regions?: string[] | string

packages/next/src/server/web/types.ts

@@ -6,6 +6,8 @@ import type { CloneableBody } from '../body-streams'
 import type { OutgoingHttpHeaders } from 'http'
 import type { FetchMetrics } from '../base-http'
 
+export type { MiddlewareConfig } from '../../build/analysis/get-page-static-info'
+
 export interface RequestData {
   geo?: {
     city?: string

test/production/middleware-typescript/app/middleware.ts

@@ -1,4 +1,9 @@
-import { NextMiddleware, NextResponse, URLPattern } from 'next/server'
+import {
+  NextMiddleware,
+  NextResponse,
+  URLPattern,
+  MiddlewareConfig,
+} from 'next/server'
 
 export const middleware: NextMiddleware = function (request) {
   const pattern = new URLPattern({
@@ -18,3 +23,9 @@ export const middleware: NextMiddleware = function (request) {
     })
   }
 }
+
+export const config: MiddlewareConfig = {
+  matchers: [],
+  regions: [],
+  unstable_allowDynamicGlobs: undefined,
+}