Sort and finalize and regular write/append handle NaT index values differently

[vasil-pashov]

Describe the bug

When the index contains NaT regular append/write throw sorting exception while sort and finalize allows NaT values in the index.

Steps/Code to Reproduce

import arcticdb
import pandas as pd
import numpy as np

ac = arcticdb.Arctic("lmdb://test")
lib = ac.get_library("test", create_if_missing=True)
df1 = pd.DataFrame({"a": [1]}, index=pd.DatetimeIndex([pd.NaT]))
lib.write("sym", df1, staged=True)
lib.sort_and_finalize_staged_data("sym") # Does not throw

lib.write("sym_2", df) # Throws

Expected Results

The two should behave the same way and not allow NaT values in the index

OS, Python Version and ArcticDB Version

Python: 3.10.11 (tags/v3.10.11:7d4cc5a, Apr 5 2023, 00:38:17) [MSC v.1929 64 bit (AMD64)]
OS: Windows-10-10.0.22631-SP0
ArcticDB: dev

Backend storage used

No response

Additional Context

No response