[format] Prevent silent truncation of inline blob reads over 2GB

[ArnavBalyan]

Purpose

• Reading blob size larger than int max, silently returns a corrupt blob.
• This is because reader casts size silently to int, anything over intmax is silently cropped instead of failure.
• Add a check and reject oversized read with a clear error.

Tests

• UT

[JingsongLi]

+1