build: fix tsconfig monorepo setup (#10028)

Should fix messed up import suggestions and simplifies all tsconfigs
through inheritance.

One main issue was that packages were inheriting `baseURL: "."` from the
root tsconfig. This caused incorrect import suggestions that start with
"packages/...".

This PR ensures that packages do not inherit this baseURL: "." property,
while ensuring the root, non-inherited tsconfig still keeps it to get
tests to work (the importMap needs it)

test/testHooks.ts

@@ -10,7 +10,12 @@ const filename = fileURLToPath(import.meta.url)
 const dirname = path.dirname(filename)
 
 export const createTestHooks = async (testSuiteName = '_community') => {
-  const tsConfigPath = path.resolve(getNextRootDir().rootDir, './tsconfig.json')
+  const rootDir = getNextRootDir().rootDir
+  const tsConfigBasePath = path.resolve(rootDir, './tsconfig.base.json')
+  const tsConfigPath = existsSync(tsConfigBasePath)
+    ? tsConfigBasePath
+    : path.resolve(rootDir, './tsconfig.json')
+
   const tsConfigContent = await readFile(tsConfigPath, 'utf8')
   const tsConfig = parse(tsConfigContent)
 
@@ -20,7 +25,7 @@ export const createTestHooks = async (testSuiteName = '_community') => {
      */
     beforeTest: async () => {
       // Delete entire .next cache folder
-      const nextCache = path.resolve(getNextRootDir().rootDir, './.next')
+      const nextCache = path.resolve(rootDir, './.next')
       if (existsSync(nextCache)) {
         await rm(nextCache, { recursive: true })
       }