Migrate @azure-rest/batch to import subpath design (#38476)

## Description

Migrates the @azure-rest/batch package to the import subpath design
pattern using `#platform/*` wildcard imports.

### Changes

- Create `config/` directory with tsconfigs extending from
`eng/tsconfigs/`
- Update `warp.config.yml` to extend base and use local tsconfigs
- Remove `polyfillSuffix` in favor of `#platform/*` wildcard imports
- Update `package.json` imports field with browser/react-native mappings
- Update `eslint.config.mjs` with `projectService: false`
- Update `vitest.browser.config.ts` to use
`eng/vitestconfigs/browser.config.ts`
- Delete old root tsconfig files

### Benefits

- Enables proper type separation with no mixing of node/dom/RN types
- Warp now references tsconfigs under the `config/` folder
- Consistent with other migrated packages (identity, storage-common,
etc.)

### Verification

- ✅ Build passes: `pnpm turbo build --filter=@azure-rest/batch...`
- ✅ TypeScript validation passes: `tsc -b --noEmit`
- ✅ Lint passes: `npm run lint`

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: deyaaeldeen

sdk/batch/batch-rest/config/tsconfig.lint.json

@@ -0,0 +1,4 @@
+{
+  "extends": "../tsconfig.json",
+  "include": ["../src", "../test", "../samples-dev", "../package.json"]
+}

sdk/batch/batch-rest/config/tsconfig.samples.json

@@ -0,0 +1,3 @@
+{
+  "extends": "../../../../eng/tsconfigs/samples.json"
+}

sdk/batch/batch-rest/config/tsconfig.snippets.json

@@ -0,0 +1,3 @@
+{
+  "extends": "../../../../eng/tsconfigs/snippets.json"
+}

sdk/batch/batch-rest/config/tsconfig.src.browser.json

@@ -0,0 +1,3 @@
+{
+  "extends": "../../../../eng/tsconfigs/src.browser.json"
+}

sdk/batch/batch-rest/config/tsconfig.src.cjs.json

@@ -0,0 +1,3 @@
+{
+  "extends": "../../../../eng/tsconfigs/src.cjs.json"
+}

sdk/batch/batch-rest/config/tsconfig.src.esm.json

@@ -0,0 +1,3 @@
+{
+  "extends": "../../../../eng/tsconfigs/src.esm.json"
+}

sdk/batch/batch-rest/config/tsconfig.src.react-native.json

@@ -0,0 +1,3 @@
+{
+  "extends": "../../../../eng/tsconfigs/src.react-native.json"
+}

sdk/batch/batch-rest/config/tsconfig.test.browser.json

@@ -0,0 +1,3 @@
+{
+  "extends": "../../../../eng/tsconfigs/test.browser.json"
+}

sdk/batch/batch-rest/config/tsconfig.test.node.json

@@ -0,0 +1,3 @@
+{
+  "extends": "../../../../eng/tsconfigs/test.node.json"
+}

sdk/batch/batch-rest/eslint.config.mjs

@@ -10,5 +10,11 @@ export default azsdkEslint.config([
       "@azure/azure-sdk/ts-package-json-main-is-cjs": "off",
       "tsdoc/syntax": "warn",
     },
+    languageOptions: {
+      parserOptions: {
+        projectService: false,
+        project: "./config/tsconfig.lint.json",
+      },
+    },
   },
 ]);