feat: add --run to llama stack build (#1156)

# What does this PR do?

--run runs the stack that was just build using the same arguments during
the build process (image-name, type, etc)

This simplifies the workflow a lot and makes the UX better for most
local users trying to get started rather than having to match the flags
of the two commands (build and then run)

Also, moved `ImageType` to distribution.utils since there were circular
import errors with its old location

## Test Plan

tested locally using the following command: 

`llama stack build --run --template ollama --image-type venv`

Signed-off-by: Charlie Doern <cdoern@redhat.com>

llama_stack/cli/stack/build.py

@@ -68,6 +68,13 @@ the build. If not specified, currently active Conda environment will be used if
             help="Print the dependencies for the stack only, without building the stack",
         )
 
+        self.parser.add_argument(
+            "--run",
+            action="store_true",
+            default=False,
+            help="Run the stack after building using the same image type, name, and other applicable arguments",
+        )
+
     def _run_stack_build_command(self, args: argparse.Namespace) -> None:
         # always keep implementation completely silo-ed away from CLI so CLI
         # can be fast to load and reduces dependencies