Add missing schema definitions for google_tag.settings configuration keys

Problem/Motivation

The Google Tag module stores several configuration keys in google_tag.settings that are not currently declared in config/schema/google_tag.schema.yml. As a result, configuration schema validation tools (e.g. Config Inspector) report missing schema errors for otherwise valid configuration.

The affected keys include:

• uri
• compact_snippet
• include_file
• rebuild_snippets
• flush_snippets
• debug_output
• _default_container (inline default container configuration)

These keys are present in exported configuration and are supported by the module, but are undocumented in the schema.

Steps to reproduce

1. Install and enable the Google Tag module.
2. Configure Google Tag settings (single-container or default configuration).
3. Export configuration or inspect google_tag.settings.
4. Run a schema validation tool (e.g. Reports → Configuration inspector).
5. Observe missing schema errors for keys listed above.

Proposed resolution

I am adding a patch that updates google_tag.schema.yml to:

• Add schema definitions for all missing google_tag.settings keys
• Document _default_container as an inline mapping that reflects the actual stored configuration
• Align the schema with the configuration written and consumed by the module

This is a schema-only change and does not modify runtime behavior.

Remaining tasks

Review the patch.

User interface changes

API changes

Data model changes