feat: Add HTTPS serving option (#1000)

# What does this PR do?

Enables HTTPS option for Llama Stack. 

While doing so, introduces a `ServerConfig` sub-structure to house all
server related configuration (port, ssl, etc.)

Also simplified the `start_container.sh` entrypoint to simply be
`python` instead of a complex bash command line.

## Test Plan

Conda: 

Run:
```bash
$ llama stack build --template together
$ llama stack run --port 8322        # ensure server starts 

$ llama-stack-client configure --endpoint http://localhost:8322
$ llama-stack-client models list
```

Create a self-signed SSL key / cert pair. Then, using a local checkout
of `llama-stack-client-python`, change
https://github.com/meta-llama/llama-stack-client-python/blob/main/src/llama_stack_client/_base_client.py#L759
to add `kwargs.setdefault("verify", False)` so SSL verification is
disabled. Then:

```bash
$ llama stack run --port 8322 --tls-keyfile <KEYFILE> --tls-certfile <CERTFILE>
$ llama-stack-client configure --endpoint https://localhost:8322  # notice the `https`
$ llama-stack-client models list
```

Also tested with containers (but of course one needs to make sure the
cert and key files are appropriately provided to the container.)

llama_stack/distribution/start_container.sh

@@ -40,8 +40,12 @@ shift
 port="$1"
 shift
 
+# Initialize other_args
+other_args=""
+
 # Process environment variables from --env arguments
 env_vars=""
+
 while [[ $# -gt 0 ]]; do
     case "$1" in
         --env)
@@ -55,6 +59,7 @@ while [[ $# -gt 0 ]]; do
             fi
             ;;
         *)
+            other_args="$other_args $1"
             shift
             ;;
     esac
@@ -93,5 +98,8 @@ $CONTAINER_BINARY run $CONTAINER_OPTS -it \
   -v "$yaml_config:/app/config.yaml" \
   $mounts \
   --env LLAMA_STACK_PORT=$port \
-  --entrypoint='["python", "-m", "llama_stack.distribution.server.server", "--yaml-config", "/app/config.yaml"]' \
-  $container_image:$version_tag
+  --entrypoint python \
+  $container_image:$version_tag \
+  -m llama_stack.distribution.server.server \
+  --yaml-config /app/config.yaml \
+  $other_args