Column capitalization

[utkarsharma2]

Description

What is the current behavior?

To achieve a first end-to-end delivery of the Snowflake optimization:
#487
#544

There was an assumption that to avoid issues with Snowflake mixed-capitalized column names, it was acceptable to convert all characters to uppercase.

1. it is not consistent with the dataframe decorator parameter: identifiers_as_lower
   

2. it does not support the use case where users may prefer to convert everything to uppercase
   

closes: #564

What is the new behavior?

The goal with this ticket is to add the following argument to both aql.dataframe and aql.load_file (snowflake-only), removing the previous identifiers_as_lower parameter:

columns_names_capitalization=["upper", "lower", "original"]

Checklist

• Replace the aql.dataframe argument identifiers_as_lower by columns_names_capitalization
• Add support for columns_names_capitalization when using load_file to Snowflake
• Have tests covering these scenarios
• Update release notes

[utkarsharma2]

Duplicate PR.