Fix failing Azure tests (#19877)

Noticed Azure tests have started failing after https://github.com/vercel/next.js/pull/19758 due to the middleware taking longer than the allotted threshold which adds unexpected logs to stderr. This attempts to resolve these test failures by increasing the allotted time for the middleware when running on Azure. 

x-ref: https://dev.azure.com/nextjs/next.js/_build/results?buildId=22617&view=logs&jobId=5ee44de4-e310-59d9-0ba5-4a271a649fb0&j=5ee44de4-e310-59d9-0ba5-4a271a649fb0&t=af3fb693-3771-5a1a-ec97-2ba4cc77f25c
x-ref: https://dev.azure.com/nextjs/next.js/_build/results?buildId=22619&view=logs&jobId=5ee44de4-e310-59d9-0ba5-4a271a649fb0&j=5ee44de4-e310-59d9-0ba5-4a271a649fb0&t=af3fb693-3771-5a1a-ec97-2ba4cc77f25c 

packages/next/next-server/lib/post-process.ts

 import { parse, HTMLElement } from 'node-html-parser'
 import { OPTIMIZED_FONT_PROVIDERS } from './constants'
 
-const MIDDLEWARE_TIME_BUDGET = 10
+const MIDDLEWARE_TIME_BUDGET =
+  parseInt(process.env.__POST_PROCESS_MIDDLEWARE_TIME_BUDGET || '', 10) || 10
 const MAXIMUM_IMAGE_PRELOADS = 2
 const IMAGE_PRELOAD_SIZE_THRESHOLD = 2500
 

run-tests.js

@@ -195,6 +195,7 @@ const configuredTestTypes = [UNIT_TEST_EXT]
             ...(isAzure
               ? {
                   HEADLESS: 'true',
+                  __POST_PROCESS_MIDDLEWARE_TIME_BUDGET: '50',
                 }
               : {}),
             ...(usePolling