Fix BaseSQLToGCSOperator approx_max_file_size_bytes

[dclandau]

When using the parquet file_format, using tmp_file_handle.tell()
always points to the beginning of the file after the data has been saved
and therefore is not a good indicator for the files current size.

closes: #25313

[boring-cyborg]

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[potiuk]

Nice.

[eladkal]

Tests are failing :(

[dclandau]

I'll have a look at it.

[dclandau]

The tests were failing because when writing bytes into the file, python buffers the data until it is flushed via the method fp.flush().
Because the file was not being flushed prior to the if statement, os.stat(fp.name).st_size was only indicating the size of the file as is in the system, without including the bytes still to be flushed.

As a quick sanity test you can run:

with open('test', 'wb') as f:
    f.write(b'hello')
    print(f.tell())
    import os
    print(os.stat(f.name).st_size)
    f.seek(0, os.SEEK_END)
    print(f.tell())
    f.flush()
    print(os.stat(f.name).st_size)

[potiuk]

Yeah. Tests are useful it seems :)