+if clause for _query_imbalance in decorators

[awarsewa]

This fixes the issue that unavailability entries are discarded because of duplicate removal in the decorators by adding an if-clause to restrict duplicate removal to all wrapped functions other than _query_imbalance.

To test, try the following code with and without this change:

from entsoe import EntsoePandasClient
import pandas as pd
import pytz
import os

start = pd.Timestamp(2024, 1, 1, tzinfo=pytz.timezone('Europe/Berlin'))
end = pd.Timestamp(2024, 1, 14, tzinfo=pytz.timezone('Europe/Berlin'))

client = EntsoePandasClient(api_key=os.getenv('ENTSOE_API_KEY'))
df = client.query_unavailability_of_generation_units('DE_LU', start=start,end=end, docstatus='A05')

Also fixes an issue with the aggregated_bids parsing function for querying TSO data that does not include activated volumes.

[fboerman]

looks good many thanks for this PR and the detailed test code!