Handling pre unix epoch timestamps

[shnayak-msft]

Description

This PR addresses an integer overflow issue in timestamp handling, particularly for dates before 1970 (unix epoch time), which are unsupported due to limitations in int64 and UnixNano usage.

Root Cause:

• UnixNano uses int64, supporting ±292 years from 1970, but our implementation only handled positive values.
• Pre-1970 timestamps failed due to incorrect use of time.Unix(0, nanoSeconds) with uint64.
• Even with signed values, the lower bound is 1678, leaving 1601–1678 unsupported.
• Additional overflow occurred in StatxTimestampToFiletime() due to unchecked arithmetic on seconds and nanoseconds.

Fix:

• Replaced Unix epoch base with Windows epoch time (1601) in nanoseconds.
• Used uint64 to represent time, extending support from 1601 to 2185.
• Preserved existing struct definitions and ensured backward compatibility.
• Implemented workarounds for Go’s time package limitations on nanosecond precision

Status:

• Manual testing passed.
• Some pipeline failures observed due to precision mismatches between Go time and filesystem time (under investigation).

Type of Change

• [x ] Bug fix
• New feature
• Documentation update required
• Code quality improvement
• Other (describe):

How Has This Been Tested?

Thank you for your contribution to AzCopy!

[gapra-msft]

Please be sure to update the schema version at the top of this file.