[blob-service] Validate holder and blob_hash inputs

Summary:
Part of ENG-3810. Used function from previous diff to validate blob service holder and blob_hash inputs.

Depends on D8179.

Test Plan: Tried to upload blob with hash blob/hash$@ - a HTTP 400 error was returned.

Reviewers: jon, varun, michal

Reviewed By: jon

Subscribers: atul, ashoat, tomek

Differential Revision: https://phab.comm.dev/D8180