BlobWriter does not implement closed property #903

Environment details

• OS type and version: Mac OS X 12.6
• Python version: python --version: 3.9.0
• pip version: pip --version: 22.2.0
• google-cloud-storage version: pip show google-cloud-storage: 2.6.0

Steps to reproduce

Run the code example below, substituting a real bucket for some-bucket.

Code example

from google.cloud import storage

client = storage.Client()
bucket = storage.Bucket.from_string("gs://some-bucket", client=client)
blob = bucket.blob('deleteme')
stream = blob.open(mode='w', ignore_flush=True)
stream.write("foobarbaz")
stream.close()
print(stream.closed) # --> False.

stream.closed should return True after stream.close() is called. I think it's probably returning False because BlobWriter is not calling super.close() and does not override IOBase.closed.

BlobReader may have a similar problem, I haven't checked.