Adding optional columns before compute with columns.

[jfarid27]

Description

Add the preprocessing step of portfolio columns before using the columns. This PR moves the optional column filling earlier into the stack so one can add a portfolio with only the basic required columns.

Issues

#2444

Motivation

Trying to add a custom overwrite into Portfolio requires users to exactly match existing columns. This is slightly annoying since some users may have their own dataset transformers or sheets, and they want to pull only the required columns. This PR helps with that.

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Ran pytests and cleared.

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[montezdesousa]

Hey! Thanks for the contribution, seems to work fine for me and solves the bug.

The approach is good, later we should add a similar check for required_fields : Date, Ticker, Type, Price, Quantity, Side and warn the user they must be there stopping pre-processing. Now it is continuing the workflow and found this case where it only stops in " Loading price data: Error: "['Type', 'Investment'] not in index" " and 'Investment' is not even required.