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)

packages/plugin-nested-docs/tsconfig.json

@@ -1,25 +1,4 @@
 {
-  "extends": "../../tsconfig.json",
-  "compilerOptions": {
-    "composite": true, // Make sure typescript knows that this module depends on their references
-    "noEmit": false /* Do not emit outputs. */,
-    "emitDeclarationOnly": true,
-    "outDir": "./dist" /* Specify an output folder for all emitted files. */,
-    "rootDir": "./src" /* Specify the root folder within your source files. */,
-    "jsx": "react-jsx"
-  },
-  "exclude": [
-    "dist",
-    "build",
-    "tests",
-    "test",
-    "node_modules",
-    "eslint.config.js",
-    "src/**/*.spec.js",
-    "src/**/*.spec.jsx",
-    "src/**/*.spec.ts",
-    "src/**/*.spec.tsx"
-  ],
-  "include": ["src/**/*.ts", "src/**/*.tsx", "src/**/*.d.ts", "src/**/*.json"],
+  "extends": "../../tsconfig.base.json",
   "references": [{ "path": "../payload" }]
 }