Change VisibilityRow execution duration type to int64

[rodrigozhou]

What changed?

Change VisibilityRow.ExecutionDuration type from *time.Duration to *int64.

Why?

time.Duration is not always translated correctly to integer values when inserting into the database (eg: jackc/pgx module with connection attributes default_query_exec_mode: simple_protocol translates time.Duration into a string instead of an integer).
Furthermore, the VisibilityRow is meant to represent the values from DB, so making it int64 also makes it more explicitly.
#10514

How did you test it?

• built
• run locally and tested manually
• covered by existing tests (updated existing tests)
• added new unit test(s)
• added new functional test(s)

Potential risks

Users implementing their own VisibilityStore based on the SQL implementation which uses the VisibilityRow might need to double check their code.

[rodrigozhou]

PR #10529 has a quick fix without changing VisibilityRow