Templating overhaul, implement Data Tagging

[nitzmahone]

Links to documentation, detailed discussion and instructions for testing can be found on the Ansible forum.

Data Tagging

• Variables and values can now carry extensible metadata tags, including provenance, template trust status, and deprecation information.
• Values tagged as Deprecated can issue runtime warnings when accessed.

Development and integration of the Data Tagging features led to the discovery of many latent security and performance issues in other parts of ansible-core, culminating in an overhaul of the templating engine and other areas:

Templating

• String values now require explicit trust to be rendered as templates.
• Rewrote Jinja integration.
• Most nested/recursive templating operations are now fully lazy, vastly improving performance in complex scenarios.

Error handling

• Standardized error handling and exception capture throughout controller and target Python code.
• Automatically provide detailed error messages with operation and source context.
• Removed many bespoke error handlers that actually masked detail.
• Traceback capture/display is no longer tied to verbosity, and can be optionally triggered at the site of any exception, warning, or error.

Test coverage

• Increased coverage, quality, and stability of integration and unit tests for numerous core features.

ISSUE TYPE

• Feature Pull Request

ADDITIONAL INFO

Draft porting guide ansible/ansible-documentation#2429

[webknjaz]

/azp run