[flutter_tools] Implement Configuration extension slice and flutter config integration - #191445

- Use firstWhere with fallback when deserializing ValidationType and ValidationMessageType from JSON in package:flutter_tools_core to handle unrecognized types gracefully.
- Use pattern matching for extensionManager in DoctorValidatorsProvider instead of bang operator.
- Add tests for unknown diagnostic enum types.

- Cache DiagnosticsExtensionClient per ExtensionConnection in ExtensionManager.
- Safely handle title and diagnostics RPC responses with try/catch and type validation.
- Pre-fetch diagnostics extension titles during Doctor.startValidatorTasks.

…ent and validation aggregation

- Initialize diagnostics extension clients and fetch titles during ExtensionManager initialization.
- Replace dynamic client map in ExtensionManager with an immutable list and assert on initialization.
- Use exhaustive switch statement for ValidationType aggregation in ExtensionDoctorValidator.
- Remove manual prefetch loop from Doctor.startValidatorTasks.

…ostics-slice

…ostics-slice

# Conflicts:
#	packages/flutter_tools/lib/executable.dart

…ostics-slice

# Conflicts:
#	packages/flutter_tools/lib/executable.dart

…onfig integration

…guration-slice

# Conflicts:
#	packages/flutter_tools/lib/src/experimental/extension_manager.dart
#	packages/flutter_tools/packages/flutter_tools_core/lib/flutter_tools_core.dart
#	packages/flutter_tools/packages/flutter_tools_extension/lib/flutter_tools_extension.dart
#	packages/flutter_tools/packages/flutter_tools_extension_linux_prototype/lib/flutter_tools_extension_linux_prototype.dart
#	packages/flutter_tools/test/commands.shard/hermetic/tool_extensions_integration_test.dart
#	packages/flutter_tools/test/integration.shard/tool_extensions_test.dart

…on slice

- Initialize dynamic options prior to argument parsing in `FlutterCommandRunner` via robust command target resolution.
- Extract `cloneParser` helper on `ExtensionArgParserMixin` for cleaner argument parser cloning.
- Enhance RPC error handling and collection parsing with pattern matching in `ConfigurationExtensionClient`.
- Simplify deserialization using Dart 3 switch expressions in `FeatureFlag` and `ConfigOption`.
- Cache configuration extensions and enforce initialization lifecycle asserts in `ExtensionManager`.

…rgParserMixin

…Flags

…estructuring

Consolidate extension settings state to _extensionSettingsGroups in `ConfigCommand`:

- Remove redundant `_extensionFeatureFlags` and `_extensionConfigOptions` fields.
- Apply object destructuring patterns across all loops iterating over `ExtensionSettingsGroup`, `FeatureFlag`, and `ConfigOption` in `extensionArgParserCacheKey`, `buildDynamicArgParser`, `runCommand`, and `settingsText`.
- Simplify dynamic parser cache key computation.

…support subcommand hierarchies

- Traverse parent command hierarchy in _initializeDynamicOptions to initialize all ExtensionArgParserMixin commands.
- Add unit tests in flutter_command_runner_test.dart for subcommands, parent flags, inline option values, empty inline values, unknown flags, negated flags, and help subcommands.