Fix installation that causes torch conflict (#13074)

Looking into resolving this:
pytorch/pytorch#159599

A package in requirements-examples.txt had a dependency on torchvision,
and we ended up installing stable release from standard pypi package.
And transitively we ended up installing stable torch and uninstalling
existing torch nightly.

We just need to swap the installation (first install domain libraries
and torch) and then necessary examples packages.

Test Plan: 

`python ./install_requirements.sh --example`

Outputs

```
(executorch_test_9) mnachin@mnachin-mbp executorch % pip freeze | grep torch
pytorch_tokenizers @ file:///Users/mnachin/executorch/extension/llm/tokenizers
torch==2.9.0.dev20250725
torchao @ file:///Users/mnachin/executorch/third-party/ao
torchaudio==2.8.0.dev20250725
torchdata==0.11.0
torchsr==1.0.4
torchtune==0.6.1
torchvision==0.24.0.dev20250725
```

Author: mergennachin

install_requirements.py

@@ -142,19 +142,6 @@ def install_requirements(use_pytorch_nightly):
 
 
 def install_optional_example_requirements(use_pytorch_nightly):
-    print("Installing packages in requirements-examples.txt")
-    subprocess.run(
-        [
-            sys.executable,
-            "-m",
-            "pip",
-            "install",
-            "-r",
-            "requirements-examples.txt",
-        ],
-        check=True,
-    )
-
     print("Installing torch domain libraries")
     DOMAIN_LIBRARIES = [
         (
@@ -178,6 +165,19 @@ def install_optional_example_requirements(use_pytorch_nightly):
         check=True,
     )
 
+    print("Installing packages in requirements-examples.txt")
+    subprocess.run(
+        [
+            sys.executable,
+            "-m",
+            "pip",
+            "install",
+            "-r",
+            "requirements-examples.txt",
+        ],
+        check=True,
+    )
+
 
 # Prebuilt binaries for Intel-based macOS are no longer available on PyPI; users must compile from source.
 # PyTorch stopped building macOS x86_64 binaries since version 2.3.0 (January 2024).