[web][native] Support fetching Blob service URIs
Summary:
This diff adds support for fetching Blob service URIs for the native and web.
Depends on D7616
Test Plan:
Uploaded both encrypted and non-encrypted blob to local blob service instance.
Amended the keyserver's upload-fetchers to return these Blob URIs.
Verified media is fetched and displayed correctly both on web and native.
Reviewers: atul, marcin, ginsu, rohan
Reviewed By: atul
Subscribers: ashoat, tomek
Differential Revision: https://phab.comm.dev/D7617