configuration: deprecate old style global state interface

All built-in west commands are using the new WestCommand.config state
to access the configuration values. Extension commands which are
reading configuration values should migrate to using this interface as
well, as should any other out of tree users of the west.configuration
API.

Deprecation, rather than removal, is necessary since 'west build' and
other important Zephyr extensions rely on the existing API.

Signed-off-by: Martí Bolívar <marti.bolivar@nordicsemi.no>

src/west/configuration.py

@@ -41,6 +41,7 @@
 import platform
 from enum import Enum
 from typing import Any, Dict, Iterable, List, Optional, Tuple, TYPE_CHECKING
+import warnings
 
 from west.util import west_dir, WestNotFound, PathType
 
@@ -391,14 +392,16 @@ def _cf_to_dict(cf: Optional[_InternalCF]) -> Dict[str, Any]:
         return ret
 
 
-# Configuration values.
-#
-# Initially empty, populated in read_config(). Always having this available is
-# nice in case something checks configuration values before the configuration
-# file has been read (e.g. the log.py functions, to check color settings, and
-# tests).
+# Global parser containing configuration values, for backwards
+# compatibility. Populated in main.py to keep legacy extensions
+# working following the deprecation of this API.
 config = _configparser()
 
+def _deprecated(old_function):
+    warnings.warn(f'{old_function} is deprecated; '
+                  'use a west.configuration.Configuration object',
+                  DeprecationWarning, stacklevel=2)
+
 def read_config(configfile: Optional[ConfigFile] = None,
                 config: configparser.ConfigParser = config,
                 topdir: Optional[PathType] = None) -> None:
@@ -426,6 +429,8 @@ def read_config(configfile: Optional[ConfigFile] = None,
     :param config: configuration object to read into
     :param topdir: west workspace root to read local options from
     '''
+    _deprecated('read_config')
+
     if configfile is None:
         configfile = ConfigFile.ALL
     config.read(_gather_configs(configfile, topdir), encoding='utf-8')
@@ -451,6 +456,8 @@ def update_config(section: str, key: str, value: Any,
       found by searching the file system (raising WestNotFound if
       one is not found).
     '''
+    _deprecated('update_config')
+
     if configfile == ConfigFile.ALL:
         # Not possible to update ConfigFile.ALL, needs specific conf file here.
         raise ValueError(f'invalid configfile: {configfile}')
@@ -494,6 +501,8 @@ def delete_config(section: str, key: str,
       found by searching the file system (raising WestNotFound if
       one is not found).
     '''
+    _deprecated('delete_config')
+
     stop = False
     if configfile is None:
         to_check = [_location(x, topdir=topdir) for x in