Eliminate hacky use of timestamps and time.sleep in tests

[kounelisagis]

In #1953, some tests were modified to ensure that TileDB-Inc/TileDB#4800 worked as intended. Previously, the timestamp argument was occasionally used for writes to avoid failures when writes occurred almost concurrently. Following that change, some tests were made temporarily conditional for error identification purposes. Over the subsequent eight months, no related test failures have remained unresolved. The only directly connected issue identified and solved during this time is #2090.

This PR removes the use of the timestamp argument where it was employed in a hacky manner and eliminates the use of time.sleep. However, not all parameterization introduced in #1953 have been reverted, as the use of use_timestamps parameter increases test coverage for scenarios where users want to utilize the time-travel capabilities provided by TileDB.