Fixes #4829: Removed `PARSING_ONLY` from `\yii\rest\UrlRule` to allow creating non-GET URLs for forms and tests

Fixes #4188: API exceptions are now exposing less data when YII_DEBUG is false

- If exception is internal it's always returned as HTTP 500 general purpose one.
- Type isn't exposed anymore.

[ci skip] Fixes typo in structure-assets.md

[ci skip] Adds start-gii-crud-preview image to the gii guide

Used a single database and a single CLI entry point for all test types. Added faker to basic app dev requirements.

structure-extensions.md translated to Russian[skip-ci]

Fix PHPDoc

fixes typos in start-databases.md

Unused InvalidConfigException