Similarly to what has been done for s3 and azure, this commit removes
the repository settings `application_name` and `connect/read_timeout`
in favor of client settings. It introduce a GoogleCloudStorageClientSettings
class (similar to S3ClientSettings) and a bunch of unit tests for that,
it aligns the documentation to be more coherent with the S3 one, it
documents the connect/read timeouts that were not documented at all and
also adds a new client setting that allows to define a custom endpoint.
a6a138905d