[Parquet][Python] Inconsistent default values for Parquet `pre_buffer`

### Describe the bug, including details regarding any error messages, version, and platform.

Some Parquet reading APIs in PyArrow have `pre_buffer` default to False and others to True.

The default value should probably be made consistent. On the C++ side, the default value is true.

### Component(s)

Python, Parquet