feat: remove usage of build yaml (#4192)

# What does this PR do?

the build.yaml is only used in the following ways:

1. list-deps
2. distribution code-gen

since `llama stack build` no longer exists, I found myself asking "why
do we need two different files for list-deps and run"?

Removing the BuildConfig and altering the usage of the
DistributionTemplate in llama stack list-deps is the first step in
removing the build yaml entirely.

Removing the BuildConfig and build.yaml cuts the files users need to
maintain in half, and allows us to focus on the stability of _just_ the
run.yaml

This PR removes the build.yaml, BuildConfig datatype, and its usage
throughout the codebase. Users are now expected to point to run.yaml
files when running list-deps, and our codebase automatically uses these
types now for things like `get_provider_registry`.

**Additionally, two renames: `StackRunConfig` -> `StackConfig` and
`run.yaml` -> `config.yaml`.**

The build.yaml made sense for when we were managing the build process
for the user and actually _producing_ a run.yaml _from_ the build.yaml,
but now that we are simply just getting the provider registry and
listing the deps, switching to config.yaml simplifies the scope here
greatly.

## Test Plan

existing list-deps usage should work in the tests.

---------

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

src/llama_stack/core/server/server.py

@@ -34,7 +34,7 @@ from pydantic import BaseModel, ValidationError
 from llama_stack.core.access_control.access_control import AccessDeniedError
 from llama_stack.core.datatypes import (
     AuthenticationRequiredError,
-    StackRunConfig,
+    StackConfig,
     process_cors_config,
 )
 from llama_stack.core.distribution import builtin_automatically_routed_apis
@@ -52,7 +52,7 @@ from llama_stack.core.stack import (
     replace_env_vars,
 )
 from llama_stack.core.utils.config import redact_sensitive_fields
-from llama_stack.core.utils.config_resolution import Mode, resolve_config_or_distro
+from llama_stack.core.utils.config_resolution import resolve_config_or_distro
 from llama_stack.core.utils.context import preserve_contexts_async_generator
 from llama_stack.log import LoggingConfig, get_logger
 from llama_stack_api import Api, ConflictError, PaginatedResponse, ResourceNotFoundError
@@ -147,7 +147,7 @@ class StackApp(FastAPI):
     start background tasks (e.g. refresh model registry periodically) from the lifespan context manager.
     """
 
-    def __init__(self, config: StackRunConfig, *args, **kwargs):
+    def __init__(self, config: StackConfig, *args, **kwargs):
         super().__init__(*args, **kwargs)
         self.stack: Stack = Stack(config)
 
@@ -369,7 +369,7 @@ def create_app() -> StackApp:
     if config_file is None:
         raise ValueError("LLAMA_STACK_CONFIG environment variable is required")
 
-    config_file = resolve_config_or_distro(config_file, Mode.RUN)
+    config_file = resolve_config_or_distro(config_file)
 
     # Load and process configuration
     logger_config = None
@@ -380,7 +380,7 @@ def create_app() -> StackApp:
         logger = get_logger(name=__name__, category="core::server", config=logger_config)
 
         config = replace_env_vars(config_contents)
-        config = StackRunConfig(**cast_image_name_to_string(config))
+        config = StackConfig(**cast_image_name_to_string(config))
 
     _log_run_config(run_config=config)
 
@@ -510,7 +510,7 @@ def create_app() -> StackApp:
     return app
 
 
-def _log_run_config(run_config: StackRunConfig):
+def _log_run_config(run_config: StackConfig):
     """Logs the run config with redacted fields and disabled providers removed."""
     logger.info("Run configuration:")
     safe_config = redact_sensitive_fields(run_config.model_dump(mode="json"))