Assert Timestamp Precision handling in round trip testing

Once we're able to complete round trip testing (write in format A, convert to B, write in B, convert back to A), we need to assert that we are not losing the precision of timestamps. This will likely involve storing some additional metadata in the target schemas.

No files or tests are named. Start by locating the round-trip testing entry point and the target schema handling for each supported table format; define completion as round trips asserting that timestamp precision is preserved, including any required schema metadata.

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