Expose blind_write in fluent-plugin-gcs

[YorithTheDreamer]

Is your feature request related to a problem? Please describe.
We are using nearline and archive clsss storage for some of the logs we are saving.

Typical operational costs are driven up dramatically by the fact the storage.object.get is being run constantly from this block in the plug in:

https://github.com/kube-logging/fluent-plugin-gcs/blob/ad6a7cb0f166e2c1648954a928e1e9b8cdcbf93d/lib/fluent/plugin/out_gcs.rb#L163-L169

Describe the solution you'd like
Expose blind_write in the gcs output struct so it can be part of the fluentd output

logging-operator/pkg/sdk/logging/model/output/gcs.go

Line 50 in 98425aa

type GCSOutput struct {

Describe alternatives you've considered
We could use a different storage class, but in the long term this would be more expensive.