Convert Status-based call sequence checks to CHECK-based.

Call sequence requirements are correctness requirements; any violation of a correctness requirement is a code defect / bug. Currently, some code in the TF GCS client uses Status objects to report call sequence violations. This tolerates bugs, allowing them to go undetected and uncorrected.

This change converts many call sequence checks to use CHECK, rather than Status. The result is code that is simpler, and that exposes bugs, rather than protecting them.

PiperOrigin-RevId: 179709047