[CICD] Github workflow for publishing Docker images (#764)

# What does this PR do?

- Add Github workflow for publishing docker images. 
- Manual Inputs
- We can use a (1) TestPyPi version / (2) build via released PyPi
version

**Notes**
- Keep this workflow manually triggered as we don't want to publish
nightly docker images

**Additional Changes**
- Resolve issue with running llama stack build in non-terminal device
```
  File "/home/runner/.local/lib/python3.12/site-packages/llama_stack/distribution/utils/exec.py", line 25, in run_with_pty
    old_settings = termios.tcgetattr(sys.stdin)
                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
termios.error: (25, 'Inappropriate ioctl for device')
```
- Modified build_container.sh to work in non-terminal environment


## Test Plan

- Triggered workflow:
3562217878
<img width="1076" alt="image"
src="https://github.com/user-attachments/assets/f1b5cef6-05ab-49c7-b405-53abc9264734"
/>


- Tested published docker image
<img width="702" alt="image"
src="https://github.com/user-attachments/assets/e7135189-65c8-45d8-86f9-9f3be70e380b"
/>


- /tools API endpoints are served so that docker is correctly using the
TestPyPi package
<img width="296" alt="image"
src="https://github.com/user-attachments/assets/bbcaa7fe-c0a4-4d22-b600-90e3c254bbfd"
/>

- Published tagged images:
https://hub.docker.com/repositories/llamastack
<img width="947" alt="image"
src="https://github.com/user-attachments/assets/2a0a0494-4d45-4643-bc29-72154ecc54a5"
/>


## Sources

Please link relevant resources if necessary.


## Before submitting

- [ ] This PR fixes a typo or improves the docs (you can dismiss the
other checks if that's the case).
- [ ] Ran pre-commit to handle lint / formatting issues.
- [ ] Read the [contributor
guideline](https://github.com/meta-llama/llama-stack/blob/main/CONTRIBUTING.md),
      Pull Request section?
- [ ] Updated relevant documentation.
- [ ] Wrote necessary unit or integration tests.

llama_stack/distribution/utils/exec.py

@@ -98,9 +98,11 @@ def run_with_pty(command):
 
 
 def run_command(command):
-    process = subprocess.Popen(command, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
-    output, error = process.communicate()
-    if process.returncode != 0:
-        log.error(f"Error: {error.decode('utf-8')}")
-        sys.exit(1)
-    return output.decode("utf-8")
+    try:
+        result = subprocess.run(command, capture_output=True, text=True, check=True)
+        print("Script Output\n", result.stdout)
+        return result.returncode
+    except subprocess.CalledProcessError as e:
+        print("Error running script:", e)
+        print("Error output:", e.stderr)
+        return e.returncode