This pull request introduces new functionality to the Google::Cloud::Storage::File class, enabling direct manipulation of an object's context. This enhancement provides greater control over file metadata, facilitating more nuanced data management within Google Cloud Storage.

Highlights

• Object Contexts Support: Introduced comprehensive support for Google Cloud Storage Object Contexts, allowing users to attach custom key-value pairs to objects for enhanced metadata management.
• Listing and Filtering: Added the ability to filter object listings based on Object Contexts, supporting queries for presence, absence, existence, and non-existence of specific context keys or key-value pairs.
• Input Validation: Implemented validation to prevent the use of forbidden characters (double quotes) in Object Context keys and values, ensuring compatibility with GCS filter string syntax.
• System and Unit Tests: Expanded test coverage with new system and unit tests to verify the functionality of Object Contexts across various scenarios, including creation, updates, copying, combining, and filtering.