Blueprints for template entities (#126971)

* Template domain blueprints

* Default blueprint for templates

* Some linting

* Template entity updates

* Load and use blueprints in config

* Added missing mapping methods for templates

* Linting

* Added tests

* Wrong schema type

* Hassfest errors

* More linting issues

* Refactor based on desired schema

In the [architecture discussion](https://github.com/home-assistant/architecture/discussions/1027), the template blueprint instance did not specify the platform (e.g. `binary_sensor`), but the initial implementation assumed that schema.

* Create default template blueprints on first run

* Moved TemplateConfig definition

This is to avoid circular references

* Corrected methods to find templates based on blueprints

* Corrected missing entity config information

* Added tests

* Don't use hass.data

Address comments https://github.com/home-assistant/core/pull/126971/#discussion_r1780097187

* Prevent creating blueprints during testing

* Combine 2 ifs

Address comment https://github.com/home-assistant/core/pull/126971/#discussion_r1780160870

* Improve test coverage

* Prevent template component from dirtying test env

* Remove useless hard-coded validation

* Improve code coverage to 100%

* Address review comments

* Moved helpers in helpers.py

As per comment https://github.com/home-assistant/core/pull/126971#discussion_r1786539889



* Fix blueprint source URL

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Co-authored-by: Martin Hjelmare <marhje52@gmail.com>