google-common [Feature]: Support File API as media/metadata store

[afirstenberg]

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Issue Content

Works on AI Studio only.

See https://ai.google.dev/api/rest/v1beta/files and https://ai.google.dev/api/rest/v1beta/media/upload
See https://github.com/google-gemini/cookbook/blob/main/quickstarts/Video.ipynb

See langchain-ai/langchain-google#147

This is an odd kind of store

• You store the media file, and get back metadata including the URL.
• Then you can use this URL for fileData messages to include the media.
• It manages the file (it will delete it after 2 days).
• There is no way to download the media, however, just the metadata.

I'd like to have this used in a couple of ways:

• As a stand-alone component so devs can save the media and manage the URL themselves (initial priority)
• As something used by the Chat module so if a file_url or media type is provided, it will save it to the File store and use the URL instead (future implementation)

What is the best interface to represent this with? In the past, @jacoblee93 has suggested subclassing BaseStore where the key is... a filename? And the value when set is just the file (in what form) and when retrieved is a Record<string,string>? I'm honestly not sure.

(I would also like a companion version, with the same interface, that words with Google Cloud Storage for use with Vertex. See #5076 )

[afirstenberg]

Being done as part of #5835