[web] Fix preloading blob service URIs

Summary:
I realized that the preloadImage and preloadMediaResource functions do not resolve Blob service URIs so preloading them would fail. This diff fixes that.

Depends on D8050

Test Plan:
Called preloadMediaResource with a blob-service://XXXX URI, observed the devtools Network tab.
Before it failed with network error, now it succeeds: the request is sent to https://blob.commtechnologies.org/XXXX

Reviewers: atul, ashoat

Reviewed By: ashoat

Subscribers: tomek

Differential Revision: https://phab.comm.dev/D8051