[SPARK-17035] [SQL] [PYSPARK] Improve Timestamp not to lose precision for all cases

## What changes were proposed in this pull request?

`PySpark` loses `microsecond` precision for some corner cases during converting `Timestamp` into `Long`. For example, for the following `datetime.max` value should be converted a value whose last 6 digits are '999999'. This PR improves the logic not to lose precision for all cases.

**Corner case**
```python
>>> datetime.datetime.max
datetime.datetime(9999, 12, 31, 23, 59, 59, 999999)
```

**Before**
```python
>>> from datetime import datetime
>>> from pyspark.sql import Row
>>> from pyspark.sql.types import StructType, StructField, TimestampType
>>> schema = StructType([StructField("dt", TimestampType(), False)])
>>> [schema.toInternal(row) for row in [{"dt": datetime.max}]]
[(253402329600000000,)]
```

**After**
```python
>>> [schema.toInternal(row) for row in [{"dt": datetime.max}]]
[(253402329599999999,)]
```

## How was this patch tested?

Pass the Jenkins test with a new test case.

Author: Dongjoon Hyun <dongjoon@apache.org>

Closes #14631 from dongjoon-hyun/SPARK-17035.